Caramel Banana Cake

Cut 4 tablespoons unsalted butter into 1/2-inch cubes.

Place 1 1/2 cups granulated sugar and 1/2 cup water in a large, heavy-bottomed saucepan over high heat. Stir with a wooden spoon until the sugar dissolves, then stop stirring and bring to a boil.

Continue to boil, swirling the pan occasionally but not stirring, until it turns a deep amber color. This will take anywhere from 6 to 15 minutes, depending on your pan and stove. You will see pale yellow streaks, then darker ones appear in the center of the bubbling sugar. When you see these, pick up the pan with the handles and swirl occasionally, and be attentive. At the very first whisp of smoke from the caramel, remove from the heat. By now it should be very dark amber. (You are looking for a dark caramel here, because you will be adding cream, so don't flinch and take it off the heat when it's still just pale gold!)

While whisking continuously, immediately but slowly pour in 2 cups heavy cream. Be very careful — the caramel is going to steam and bubble up violently! Add the butter and 1/2 teaspoon fine or 1 teaspoon kosher salt and whisk smooth. Return to medium heat and simmer for 5 minutes to slightly reduce. Let cool completely before using.

Make the cake layers: Place 1 1/2 sticks unsalted butter in the bowl of a stand mixer or in a large bowl if using an electric hand mixer. Let sit at room temperature until softened, at least 1 hour.

Arrange 2 racks to divide the oven into thirds and heat the oven to 325°F. Line the bottoms of 3 (9-inch) round cake pans parchment paper, then coat the paper and sides of the pan with cooking spray or butter. (If you only have 2 cake pans, bake in 2 rounds on the middle rack.)

Place 3 cups all-purpose flour, 1 1/2 teaspoons baking soda, and 1/2 teaspoon fine salt or 1 teaspoon kosher salt in a medium bowl and whisk to combine. Place 1 1/2 cups mashed banana, 1 1/2 cups milk, and 2 teaspoons vanilla extract in a large bowl and whisk to combine.

Add 3/4 cup granulated sugar and 3/4 cup packed light or dark brown sugar to the bowl of butter. Beat with the paddle attachment on medium speed until lightened in color and fluffy, about 4 minutes. Beat in 3 large eggs one at a time until silky and lightened in color. Stop the mixer and scrape down the sides of the bowl.

With the mixer on the lowest speed, add half of the banana mixture and beat until just combined, then add half of the flour mixture and beat until just combined. Repeat with the remaining banana mixture, and end with the remaining flour mixture.

Transfer the batter into the prepared pans, a scant 3 cups per pan. (Use this tip for dividing the batter evenly between cake pans.) Spread the batter into an even layer all the way to the edges. Dollop 1/2 cup caramel sauce into each pan, then swirl it into the batter with a knife.

Bake until a tester inserted into the center of a cake comes out clean, 30 to 35 minutes. Place the pans on a wire rack and let the cakes cool completely in the pans. (If you are baking in 2 rounds, let one cake layer cool 5 minutes, then remove from the pan. Clean, line, and grease the pan before reusing.)

Assemble the cake: Run a thin knife around each cooled cake. Flip out of the pans and remove the parchment.

Place one cake layer on a serving plate or cake stand. Spread 1/2 cup of the caramel frosting in a thin layer on the cake. Top with the second cake layer and spread with another 1/2 cup of the caramel frosting. Top with the final cake layer and spread the remaining frosting on top in a thicker, swirled layer.

If decorating with banana, cut 1 large banana at a slight angle into 1/4-inch thick slices. Dip each slice in the remaining 1 cup caramel sauce and place around the top of the cake, overlapping the slices slightly (if the caramel is too thick to dip into, rewarm slightly first). Drizzle the whole cake with any remaining caramel sauce or serve on the side.

Place 1 stick unsalted butter in the bowl of a stand mixer and let sit at room temperature until softened. (Alternatively, use a large bowl and electric hand mixer.)

Add 1/2 cup caramel sauce, 1 teaspoon vanilla extract, and 1/4 teaspoon fine salt or 1/2 teaspoon kosher salt to the butter. Beat with the paddle attachment on medium speed until smooth and lightened in color, about 2 minutes.

With the mixer on low speed, slowly beat in 1 1/2 cups powdered sugar. Continue beating on medium speed until very smooth and lightened, 3 to 5 minutes more.