Sour Cherry Cake

• 1 pound tart cherries, pitted
• ¾ cup, plus 2 tablespoons sugar
• 2 tablespoons water
• 2 cups unbleached all-purpose flour
• 2 teaspoons baking powder
• ¼ teaspoon salt
• ½ cup (1 stick) unsalted butter, at room temperature, plus more for pan
• 3 large eggs, separated
• ½ teaspoon vanilla extract
• ½ cup milk
• ¼ teaspoon cream of tartar

Heat oven to 350°. Butter a 9-inch springform pan with 2-inch-high sides.
Combine cherries, 1 tablespoon of the sugar and water in a large skillet and bring to a simmer over medium heat; cook, stirring frequently, until cherries are tender, about 10 minutes. Remove from heat.
In a medium bowl, whisk together flour, baking powder and salt. Using an electric mixer, beat ¾ cup sugar and butter in a large bowl until light and fluffy, about 1 minute. Add egg yolks, one at a time, beating well after each addition; beat in vanilla. In 3 additions, mix in dry ingredients alternately with milk just until combined.
Using a clean bowl and beaters, beat egg whites and cream of tarter to stiff, but not dry, peaks. With a rubber spatula, fold ¼ of the whites into the batter to lighten, then fold remaining whites into batter.
Pour batter into pan and cover top with half of the cherries and half of their juice. Sprinkle top of batter with remaining tablespoon sugar. Bake cake until golden and tester inserted comes out clean, about 50 minutes. Remove from oven and run a small knife around edges of cake to loosen. Let cool on rack before serving with reserved cherries