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Upside-Down Caramelized Shallot and Onion Tart

By Annie Petito

Published on September 23, 2024

Time

2¼ hours

Yield

Serves 4 as a main dish or 6 as an appetizer or side dish

Upside-Down Caramelized Shallot and Onion Tart

Ingredients

1 sheet puff pastry, thawed9 large shallots (1 1⁄4 pounds)1 tablespoon extra-virgin olive oil 3⁄4 teaspoon plus 1⁄8 teaspoon table salt, divided1⁄2 teaspoon plus 1⁄8 teaspoon pepper, divided1 pound onions, halved and sliced through root end 1⁄4 inch thick1⁄2 cup water, plus more as needed2 tablespoons unsalted butter, dividedPinch baking soda 2 teaspoons minced fresh thyme 1⁄2 cup cider vinegar 2 tablespoons sugar 1 Whipped Boursin recipe

Before You Begin

Thaw frozen puff pastry in the refrigerator for 24 hours or on the counter for 30 to 60 minutes. If your puff pastry sheet accommodates a 10-inch circle, skip the rolling in step 1. Look for shallots that measure 3½ to 4 inches long and 1½ to 2 inches wide. If you get a “double” shallot, separate the lobes and halve each lengthwise to create a cut surface. We like to serve this tart with Whipped Boursin or Chive Crème Fraîche.

Instructions

  1. Adjust oven rack to middle position and heat oven to 400 degrees. Roll pastry into 10-inch square on lightly floured counter. Using plate, bowl, or skillet lid as template, cut out 10-inch round. Discard trimming. Poke pastry round all over with paring knife, then transfer round to large plate. Refrigerate until needed.
  2. Trim stem ends of shallots and halve from root end to stem end, leaving skin intact. Trim root ends but leave intact. Brush cut sides with oil and sprinkle with ⅛ teaspoon salt and ⅛ teaspoon pepper. Arrange cut side down on rimmed baking sheet and roast until tender and paring knife meets no resistance when slipped into center, 30 to 33 minutes.
  3. While shallots roast, bring onions, water, 1 tablespoon butter, baking soda, ¼ teaspoon salt, and ¼ teaspoon pepper to simmer in 10-inch ovensafe skillet over medium-high heat. Cover and cook until water has evaporated and onions start to sizzle, 10 to 12 minutes.
  4. Uncover and, using wooden spoon, spread onions into even layer, pressing into sides and bottom of skillet. Cook, without stirring, for 30 seconds. Stir onions, then spread into even layer, pressing into sides and bottom of skillet. Repeat until dark fond develops in pan. When fond develops, add 1 to 2 tablespoons water, scrape up browned bits, and stir into onions. Repeat process of letting fond develop and deglazing until onions are very soft, well browned, and slightly sticky, 10 to 12 minutes. Stir in thyme and transfer onions to bowl. (Onions can be refrigerated for up to 3 days or frozen for up to 1 month.)
  5. In now-empty skillet, bring vinegar, sugar, and remaining ½ teaspoon salt and ¼ teaspoon pepper to simmer over medium-high heat, swirling skillet to dissolve sugar. Simmer vigorously, swirling skillet occasionally, until consistency resembles that of maple syrup, 3 to 4 minutes. Stir in remaining 1 tablespoon butter. Remove skillet from heat.
  6. Gently remove outer shallot skin. Arrange shallots, cut side down, in circular pattern around edge of skillet, nestling shallots snugly. Tuck remaining shallots into center (it is not necessary to maintain circular pattern in center; it's OK if 1 or 2 pieces don't fit). Spread caramelized onions evenly over top of shallots, leaving outer inch of shallots exposed. Place pastry round on top. Bake until pastry is puffed, crisp, and deep golden brown, 35 to 38 minutes, rotating skillet halfway through baking.
  7. Let tart cool for 8 minutes. Run paring knife around edge of crust to loosen, then invert plate over skillet. Using pot holders, swiftly and carefully invert tart onto plate (if shallots shift or stick to skillet, rearrange with spoon). Let cool for at least 15 minutes. Serve warm or at room temperature. Cut into wedges.

Upside-Down Caramelized Shallot and Onion Tart

Save

Time

2¼ hours

Yield

Serves 4 as a main dish or 6 as an appetizer or side dish

Ingredients

1 sheet puff pastry, thawed
9 large shallots (1 1⁄4 pounds)
1 tablespoon extra-virgin olive oil
3⁄4 teaspoon plus 1⁄8 teaspoon table salt, divided
1⁄2 teaspoon plus 1⁄8 teaspoon pepper, divided
1 pound onions, halved and sliced through root end 1⁄4 inch thick
1⁄2 cup water, plus more as needed
2 tablespoons unsalted butter, divided
Pinch baking soda
2 teaspoons minced fresh thyme
1⁄2 cup cider vinegar
2 tablespoons sugar
1 Whipped Boursin recipe

Test Kitchen Techniques

Ingredients

1 sheet puff pastry, thawed
9 large shallots (1 1⁄4 pounds)
1 tablespoon extra-virgin olive oil
3⁄4 teaspoon plus 1⁄8 teaspoon table salt, divided
1⁄2 teaspoon plus 1⁄8 teaspoon pepper, divided
1 pound onions, halved and sliced through root end 1⁄4 inch thick
1⁄2 cup water, plus more as needed
2 tablespoons unsalted butter, divided
Pinch baking soda
2 teaspoons minced fresh thyme
1⁄2 cup cider vinegar
2 tablespoons sugar
1 Whipped Boursin recipe

Test Kitchen Techniques

Ingredients

1 sheet puff pastry, thawed
9 large shallots (1 1⁄4 pounds)
1 tablespoon extra-virgin olive oil
3⁄4 teaspoon plus 1⁄8 teaspoon table salt, divided
1⁄2 teaspoon plus 1⁄8 teaspoon pepper, divided
1 pound onions, halved and sliced through root end 1⁄4 inch thick
1⁄2 cup water, plus more as needed
2 tablespoons unsalted butter, divided
Pinch baking soda
2 teaspoons minced fresh thyme
1⁄2 cup cider vinegar
2 tablespoons sugar
1 Whipped Boursin recipe

Test Kitchen Techniques

Why This Recipe Works

Roasted shallots, caramelized onions, and crisp, buttery pastry added up to an elegant savory upside-down tart. Roasting halved shallots with their skins on let them caramelize deeply on the cut side while ensuring that they turned tender and stayed moist. The skins were easy to pluck off once the shallots were cool. To quickly caramelize onions, we used a two-stage process: Steaming them with water, butter, and baking soda helped them quickly collapse and shed their own moisture. Next, cooking them uncovered encouraged the water to evaporate and the onions to quickly and deeply brown. Reducing cider vinegar and sugar to a syrup and finishing it with butter added brightness and shine to the finished tart. We arranged the precooked shallots snugly in a circular pattern for an attractive appearance before topping them with the caramelized onions and commercial puff pastry, which tasted great and made the tart easy to execute. When the pastry was deeply browned and crisp, we let the tart rest before and after inverting, giving everything time to set up so it sliced cleanly. We like to top this tart with a cool, creamy dollop of crème fraîche with chives or Boursin with sour cream which can add tangy richness and help offset the sweet, cooked flavors of the tart.

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Before You Begin

Thaw frozen puff pastry in the refrigerator for 24 hours or on the counter for 30 to 60 minutes. If your puff pastry sheet accommodates a 10-inch circle, skip the rolling in step 1. Look for shallots that measure 3½ to 4 inches long and 1½ to 2 inches wide. If you get a “double” shallot, separate the lobes and halve each lengthwise to create a cut surface. We like to serve this tart with Whipped Boursin or Chive Crème Fraîche.

Instructions

  1. Adjust oven rack to middle position and heat oven to 400 degrees. Roll pastry into 10-inch square on lightly floured counter. Using plate, bowl, or skillet lid as template, cut out 10-inch round. Discard trimming. Poke pastry round all over with paring knife, then transfer round to large plate. Refrigerate until needed.
  2. Trim stem ends of shallots and halve from root end to stem end, leaving skin intact. Trim root ends but leave intact. Brush cut sides with oil and sprinkle with ⅛ teaspoon salt and ⅛ teaspoon pepper. Arrange cut side down on rimmed baking sheet and roast until tender and paring knife meets no resistance when slipped into center, 30 to 33 minutes.
  3. While shallots roast, bring onions, water, 1 tablespoon butter, baking soda, ¼ teaspoon salt, and ¼ teaspoon pepper to simmer in 10-inch ovensafe skillet over medium-high heat. Cover and cook until water has evaporated and onions start to sizzle, 10 to 12 minutes.
  4. Uncover and, using wooden spoon, spread onions into even layer, pressing into sides and bottom of skillet. Cook, without stirring, for 30 seconds. Stir onions, then spread into even layer, pressing into sides and bottom of skillet. Repeat until dark fond develops in pan. When fond develops, add 1 to 2 tablespoons water, scrape up browned bits, and stir into onions. Repeat process of letting fond develop and deglazing until onions are very soft, well browned, and slightly sticky, 10 to 12 minutes. Stir in thyme and transfer onions to bowl. (Onions can be refrigerated for up to 3 days or frozen for up to 1 month.)
  5. In now-empty skillet, bring vinegar, sugar, and remaining ½ teaspoon salt and ¼ teaspoon pepper to simmer over medium-high heat, swirling skillet to dissolve sugar. Simmer vigorously, swirling skillet occasionally, until consistency resembles that of maple syrup, 3 to 4 minutes. Stir in remaining 1 tablespoon butter. Remove skillet from heat.
  6. Gently remove outer shallot skin. Arrange shallots, cut side down, in circular pattern around edge of skillet, nestling shallots snugly. Tuck remaining shallots into center (it is not necessary to maintain circular pattern in center; it's OK if 1 or 2 pieces don't fit). Spread caramelized onions evenly over top of shallots, leaving outer inch of shallots exposed. Place pastry round on top. Bake until pastry is puffed, crisp, and deep golden brown, 35 to 38 minutes, rotating skillet halfway through baking.
  7. Let tart cool for 8 minutes. Run paring knife around edge of crust to loosen, then invert plate over skillet. Using pot holders, swiftly and carefully invert tart onto plate (if shallots shift or stick to skillet, rearrange with spoon). Let cool for at least 15 minutes. Serve warm or at room temperature. Cut into wedges.

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