Ingredients
Method
Toss 1 lb. fresh or frozen pitted sour cherries (about 3 cups) with ⅔ cup (134 g) sugar and 1 tsp. almond extract in a small mixing bowl and let stand at least 2 hours. Drain cherries, reserving ½ cup cherry juices.
Preheat oven to 350°F. Butter and flour a 13x9-inch metal baking pan, knocking out excess flour. Whisk together 1 cup boiling water and ¾ cup unsweetened cocoa powder (not Dutch-process) in a small bowl until smooth, then whisk in reserved cherry juices and 1 tsp. vanilla extract.
Whisk 2 cups (250 g) all-purpose flour, 1¼ tsp. baking soda, and ½ tsp. Diamond Crystal or ¼ tsp. Morton kosher salt in another small bowl.
Beat 2 sticks (1 cup) unsalted butter, softened with 1¼ cups (250 g) packed dark brown sugar in a large bowl with an electric mixer at medium speed until pale and fluffy, about 3 minutes. Add 4 large eggs, one egg at a time, beating well after each addition. Add flour mixture and cocoa mixture alternately in batches, beginning and ending with flour mixture and mixing at low speed until blended (batter may look curdled).
Pour batter into pan, smoothing top, and scatter the reserved cherries and 1 cup (7 oz.) semisweet chocolate chips evenly over the batter (they’ll sink as it bakes). Bake in middle of oven until a toothpick or tester inserted in center comes out clean, 35 to 40 minutes. Cool cake completely in pan on a rack, then cut into squares. If using, dust with powdered sugar and serve with whipped cream. Do ahead: The chocolate-covered cherry flavor of this cake becomes more pronounced after a day or two. Cake can be made up to 3 days ahead and kept in an airtight container at room temperature.