Name: Tuna with Sweet-and-Sour Onions
Total time: 50 min
Cuisine: Italian
Ingredients: 1½ pounds red onions , halved and sliced thin; ⅓ cup water; ¼ cup extra-virgin olive oil , plus extra for drizzling; ¼ teaspoon red pepper flakes; Salt and pepper; 7 teaspoons sugar; ½ cup red wine vinegar; ½ cup minced fresh mint; 4 (4- to 6-ounce) tuna steaks , about 1 inch thick

Why This Recipe Works

The waters of Sicily are famed for their tuna and swordfishing industries, while early Arab rule brought North African ingredients and flavors to the island, including agrodolce—the sour-sweet profile. A great tonno all'agrodolce is all about achieving a sauce that has the perfect balance of vinegar and sugar and is bulked up with plenty of sautéed onions. We started with the onions, drawing out their moisture by adding water and cooking them covered; this allowed us to get good browning quickly once we lifted the lid. Adding the sugar for our sauce to the onions during the last few minutes of cooking encouraged extra caramelization. After much tinkering and tasting, we found the right amount of red wine vinegar (½ cup), added it to our caramelized onions, and reduced it to intensify its flavor but mellow its bite. We tossed in mint, a classic addition, off the heat to keep it fresh and bright. Recipes call for cooking the tuna to varying degrees, from rare to well-done throughout. We typically like our tuna rare, but in this application we preferred it cooked to medium-rare so there was some contrast between the flesh and the soft texture of our onions.

Before You Begin

We prefer the tuna cooked to medium-rare here. If you like your tuna rare, cook the tuna just 1 to 2 minutes per side until it's translucent red at the center and registers 110 degrees. Only purchase tuna steaks that are deep purplish red, firm to the touch, and devoid of any “fishy” odor.

Instructions

Bring onions, water, 1 tablespoon oil, pepper flakes, and ½ teaspoon salt to boil in 12-inch nonstick skillet over high heat. Cover and cook until water has evaporated and onions start to sizzle, 5 to 7 minutes. Uncover, reduce heat to medium-high, and continue to cook until onions begin to brown, 7 to 10 minutes.

Sprinkle onions with sugar and cook, stirring occasionally, until well browned, about 3 minutes. Stir in vinegar and cook until mostly evaporated, about 1 minute. Off heat, stir in 2 tablespoons oil and ⅓ cup mint. Transfer to bowl and cover to keep warm. Wipe skillet clean with paper towels.

Pat tuna steaks dry with paper towels and season with salt and pepper. Heat remaining 1 tablespoon oil in now-empty skillet over medium-high heat until just smoking. Place tuna in skillet and cook until well browned and reddish pink at center when checked with tip of paring knife and registers 125 degrees (for medium-rare), 2 to 3 minutes per side.

Transfer onion sauce to serving dish and nestle tuna steaks on top. Drizzle with oil and sprinkle with remaining mint. Serve.