Instructions

Place milk and 3 tablespoons butter in 4-cup liquid measuring cup. Heat in microwave for 1 minute. Stir mixture with rubber spatula. Continue to heat in microwave until butter is melted, about 1 minute. Remove from microwave and let milk mixture cool until just warm, about 20 minutes.
While milk mixture cools, in medium bowl, whisk together sugar, brown sugar, and cinnamon. Measure 3 tablespoons cinnamon sugar into bowl of stand mixer. Set aside remaining cinnamon sugar mixture to use in steps 8 and 11.
Add flour, yeast, and salt to stand mixer bowl with cinnamon sugar and whisk until combined. Lock bowl into place and attach dough hook to stand mixer
When milk mixture is just warm, add egg yolks to liquid measuring cup and whisk until combined.
Start mixer on low speed and slowly pour in milk mixture. Mix until no dry flour is visible, about 2 minutes. Increase speed to medium and knead dough for 8 minutes. Stop mixer.
Transfer dough to clean counter and knead dough for 30 seconds, then form dough into smooth ball.
Spray large bowl with vegetable oil spray. Place dough in greased bowl and cover with plastic wrap. Let dough rise until doubled in size, 1 to 1½ hours.
Spray inside bottom and sides of 8½-by-4½-inch metal loaf pan with vegetable oil spray. Transfer dough to clean counter and shape, fill, and roll up dough following photos, “Step-by-Step: How to Shape Cinnamon Swirl Bread,” below.
Spray sheet of plastic with vegetable oil spray. Cover loaf pan loosely with greased plastic and let dough rise at room temperature until dough is level with top edge of pan, 30 to 45 minutes.
While dough rises, adjust oven rack to middle position and heat oven to 350 degrees.
When dough is ready, melt remaining 1 tablespoon butter in small microwave-safe bowl. Discard plastic from loaf pan. Use pastry brush to gently brush top of loaf with melted butter. Sprinkle evenly with remaining cinnamon sugar.
Place loaf pan in oven. Bake until top is deep brown, 45 to 55 minutes. Use oven mitts to remove pan from oven and place on cooling rack (ask an adult for help). Let bread cool in pan for 15 minutes.
Carefully run butter knife around edges of bread to loosen from loaf pan (ask an adult for help—pan will be hot). Use oven mitts to carefully turn pan on its side and remove bread from pan. Let bread cool completely on cooling rack, about 2 hours. Transfer bread to cutting board, slice (ask an adult for help), and serve. (Bread can be stored in airtight container at room temperature for up to 3 days.)