Spread chopped cherries onto a layer of paper towels; let stand for 20 minutes.

Preheat oven to 350°F (180°C). Spray 3 (8-inch) round cake pans with baking spray with flour. Line bottom of pans with parchment paper.

In the bowl of a stand mixer, whisk together 3 cups (375 grams) flour, sugar, baking powder, salt, and baking soda by hand. Add butter; using the paddle attachment, beat at medium-low speed until butter is incorporated and mixture resembles coarse meal, about 2 minutes.

In a medium bowl, whisk together milk, egg whites, sour cream, and vanilla extract. With mixer on low speed, add one-third of milk mixture (about ⅔ cup or 180 grams) to flour mixture, beating until combined. Increase mixer speed to medium, and beat until light and fluffy, 1 to 2 minutes. With mixer on low speed, gradually add remaining milk mixture, beating until combined and stopping to scrape paddle and bottom and sides of bowl.

In a small bowl, stir together chopped cherries and remaining 2 tablespoons (16 grams) flour. Fold into batter until just combined. Divide batter among prepared pans (about 2 cups or 575 grams each).

Bake until a wooden pick inserted in center comes out clean, 35 to 40 minutes. Let cool in pans for 10 minutes. Remove from pans, and let cool completely on wire racks.

Level cooled cake layers, if desired. Place 1 cake layer on a serving plate. Spread ¾ cup (202 grams) Vanilla Buttercream onto cake. Top with second cake layer; spread ¾ cup (202 grams) buttercream onto cake layer. Top with remaining cake layer. Spread remaining buttercream on top and sides of cake. Refrigerate for at least 15 minutes before serving. Serve with Cherry Compote. Cover and refrigerate for up to 3 days.