In traditional upside-down cake recipes, the fruit is first caramelized in a skillet. In our simplified version, the butter and sugar are creamed and spread into the cake pan; then the fruit is layered over the mixture and topped with cake batter.
1 stick unsalted butter, room temperature, plus more for pan
1 1/4 cups sugar
5 to 6 medium fresh apricots (about 1 pound), halved and pitted
12 ounces fresh sweet cherries (such as Bing), stemmed, pitted, and halved
3/4 cup all-purpose flour
1/4 cup plus 2 tablespoons fine yellow cornmeal
1 teaspoon baking powder
1/2 teaspoon salt
1/4 cup almond paste (not marzipan), crumbled
3 large eggs, separated
1/4 teaspoon pure vanilla extract
1/2 teaspoon pure almond extract
1/2 cup milk
Preheat the oven to 350°F. Butter an 8-by-3-inch round cake pan, and line bottom with parchment paper. In the bowl of an electric mixer fitted with the paddle attachment, beat 2 tablespoons butter with 1/4 cup sugar on medium speed until light and fluffy, about 2 minutes. Spread evenly over bottom of prepared pan. Arrange apricot halves, cut sides down, in pan. Fit cherries into any gaps between apricots. Pack down the fruit slightly with your hands; set aside.
In a medium bowl, whisk together flour, cornmeal, baking powder, and salt; set aside. In the bowl of an electric mixer fitted with the paddle attachment, beat remaining 6 tablespoons butter until smooth, about 1 minute. Add almond paste and 3/4 cup sugar, and beat until light and fluffy, about 2 minutes, scraping down the sides of the bowl as needed. Add the egg yolks, and beat until well combined. Beat in vanilla and almond extracts. Add the flour mixture in two parts, alternating with the milk and beginning and ending with the flour; beat until combined, and set aside.
In the clean bowl of an electric mixer fitted with the whisk attachment, beat egg whites on medium speed until foamy. Gradually sprinkle in the remaining 1/4 cup sugar, and beat until soft peaks form. Fold a third of egg-white mixture into the batter with a spatula. Gently fold in remaining egg whites.
Spread batter over fruit, smoothing with an offset spatula. Bake, rotating pan halfway through, until a cake tester inserted in the center comes out clean, 1 hour to 1 hour 10 minutes. Transfer pan to a wire rack to cool slightly, about 15 minutes. Run a knife or small offset spatula around the edges to loosen, and invert cake onto a serving plate to cool completely. Cake can be kept at room temperature, loosely covered with foil, for up to 3 days.