For Crust: Heat oven to 400 degrees F. In a mixing bowl sift together flour, sugar, baking powder, and salt. Using a pastry blender cut in the butter pieces until the mixture forms small even crumbs. Press a layer of the mixture on the bottom and halfway up the sides of an 8-inch square baking pan.
Scatter the prepared cherries on the crust. Stir together the sugar and cinnamon; sprinkle evenly over cherries. Bake for 15 minutes.
For Topping: While crust and cherries are baking, whisk together the egg yolks and sour cream. Right after baking for the 15 minutes, remove from oven and immediately pour sour cream mixture evenly over the top. Return to oven and bake an additional 25 minutes or until the top starts to lightly brown. Remove and cool completely on a wire rack. Cut into squares to serve. It can be served at room temperature or refrigerated until cold. It's great both ways!
Recipe by The Culinary Cellar at https://theculinarycellar.com/cherry-kuchen/