Fruit Skillet Cake

Preheat oven to 375 degrees F. Butter an 8-inch ovenproof skillet (preferably cast iron), and dust with flour. Whisk together flour, baking powder, baking soda, and salt. With an electric mixer on medium, beat butter and 3/4 cup sugar until pale and fluffy, 3 to 5 minutes. Beat in egg. Add flour mixture in 3 batches, alternating with buttermilk; beat until combined.

Transfer batter to the prepared skillet; smooth top. Arrange plums on top, fanning the slices; sprinkle with the remaining 2 tablespoons sugar.

Bake until golden brown and a cake tester into center comes out clean, 35 to 40 minutes. Transfer to a wire rack to cool slightly before serving.