Apple Upside-Down Cake

You will need a 9-inch nonstick cake pan with sides that are at least 2 inches tall. Alternatively, use a 10-inch ovensafe skillet (don’t use cast iron) to both cook the apples and bake the cake, with the following modifications: Cook the apples in the skillet and set them aside while mixing the batter (it’s fine if the skillet is still warm when the batter is added) and increase the baking time by 7 to 9 minutes. If you don’t have either a 2-inch-high cake pan or an ovensafe skillet, use an 8-inch square pan.

1. FOR THE TOPPING: Grease 9-inch round nonstick cake pan, line with parchment paper, grease parchment, and flour pan. Adjust oven rack to lowest position and heat oven to 350 degrees.
2. Halve apples from stem to blossom end. Cut 2 apples into 1⁄4-inch-thick slices; set aside. Cut remaining 2 apples into 1⁄2-inch-thick slices. Melt butter in 12-inch skillet over medium-high heat. Add 1⁄2-inch-thick apple slices and cook, stirring 2 or 3 times, until apples begin to caramelize, 4 to 6 minutes (do not fully cook apples). Add 1⁄4-inch-thick apple slices, brown sugar, and lemon juice and continue cooking, stirring constantly, until sugar dissolves and apples are coated, about 1 minute longer. Transfer apple mixture to prepared pan and lightly press into even layer.
3. FOR THE CAKE: Whisk flour, cornmeal, if using, baking powder, and salt together in medium bowl. Whisk granulated sugar, brown sugar, and eggs together in large bowl until thick and thoroughly combined, about 45 seconds. Slowly whisk in butter until combined. Add sour cream and vanilla and whisk until combined. Add flour mixture and whisk until just combined. Pour batter into pan and spread evenly over fruit. Bake cake until golden brown and toothpick inserted in center comes out clean, 35 to 40 minutes.
4. Let cake cool in pan on wire rack for 20 minutes. Run paring knife around sides of cake to loosen. Place wire rack over pan and, holding rack tightly, invert cake pan and wire rack together. Lift off pan. Place wire rack with cake over baking sheet or large plate to catch any drips. If any fruit sticks to pan bottom, remove and position it on top of cake. Let cake cool completely, about 20 minutes, then transfer to serving platter and serve.

APPLE UPSIDE-DOWN CAKE WITH ALMONDS
You will need 1⁄4 cup whole almonds to make 1⁄3 cup ground almonds. To grind the almonds, process them in a food processor for about 45 seconds.
Whisk 1⁄3 cup finely ground toasted almonds with flour, baking powder, and salt and add 1 teaspoon almond extract to batter with sour cream and vanilla in step 3.

APPLE UPSIDE-DOWN CAKE WITH LEMON AND THYME
Add 1 teaspoon grated lemon zest and 1 teaspoon finely chopped fresh thyme to batter with sour cream and vanilla in step 3.