Arrange a rack in center of oven; preheat to 425°. Melt ½ cup (1 stick) butter in small bowl in a microwave and let cool. Finely grate zest of whole lemon, then squeeze 2 Tbsp. juice; set aside.
Brush 1 Tbsp. melted butter around bottom and sides of cake pan (if you don’t have a pastry brush, use your fingertips). Line bottom of pan with a circle of parchment paper, smoothing to eliminate air bubbles between parchment and pan.
Toss cherries, 2 Tbsp. sugar, 2 Tbsp. lemon juice, and 2 Tbsp. melted butter in cake pan.
Bake cherries, gently shaking pan once halfway through, until fruit juices are thick and bubbling around sides of pan, 40 minutes. Let cool. Reduce oven temperature to 350°.
Whisk flour, baking powder, salt, baking soda, and 1 cup sugar in a large bowl.
Make a well in the center of dry ingredients. Beat 3 eggs to blend and pour into center of well along with 1 cup sour cream, 2 tsp. lemon zest, and remaining 5 Tbsp. melted butter.
Starting in the center, whisk to blend egg mixture, then make larger circles outward to incorporate dry ingredients. Whisk several more times until batter is smooth.
Carefully dollop large spoonfuls of batter over fruit (it’s okay if pan is still warm and some fruit juices pool around batter); gently smooth surface.
Bake cake until top is golden brown and a tester or toothpick inserted into the center comes out clean, 45–55 minutes.
Let cake cool in pan 10 minutes, then use a paring knife to loosen cake from edge of pan.
Place a wire rack or cake plate over pan, then swiftly invert rack and pan; cake should release from pan on its own. Lift cake pan off cake and peel off parchment. If some of the cherries cling to the parchment, tuck them back into place. Let cake cool completely.
Whisk remaining 1 cup sour cream with 1–2 Tbsp. sugar in a large bowl. Dollop on each slice before serving.