Preheat the oven to 350°F (180°C) and line an 8x8-inch baking pan with parchment paper, leaving an overhang on the sides to lift the finished cake out. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, cream butter and sugar together at medium speed until light and fluffy, about 4-5 minutes.
½ cup unsalted butter, ½ cup granulated sugar
Add one egg at a time and mix for 20 seconds after each addition. Add vanilla extract. Mix until combined. Scrape the bottom and sides of the bowl as needed with a rubber spatula.
3 large eggs, 2 teaspoons vanilla extract
In a small bowl, combine flour, baking powder, and salt.
1 ½ cups cake flour, 2 teaspoons baking powder, ¼ teaspoon salt
With the mixer running at medium speed, alternately add the flour mixture and milk in two portions. Mix until just combined. Don't overmix.
2 tablespoons milk
Pour batter into prepared pan and spread evenly. Top with cherries and spread evenly.
1 cup sour cherries
Bake for about 30-40 minutes, or until a toothpick inserted in the center comes out clean with only a few moist crumbs attached. Let the cake rest for about 10 minutes, then transfer to a cooling rack. Serve dusted with powdered sugar.