- Topping:
- 3 tablespoons butter, at room temperature
- 1/4 cup brown sugar (such as muscovado)
- 4 fresh nectarines, sliced into bite-size pieces
- Cake:
- 2 cups all-purpose flour
- 1 teaspoon baking powder
- 3/4 teaspoon salt
- 11 tablespoons unsalted butter, at room temperature
- 1/2 cup white sugar
- 2 large eggs
- 2 teaspoons vanilla extract
- Preheat oven to 340 degrees F (170 degrees C). Place butter in a 9-inch round cake pan and melt in the oven as it preheats.
- Remove pan from oven and sprinkle brown sugar evenly over melted butter. Arrange nectarine pieces on the brown sugar layer.
- Gently whisk flour, baking powder, and salt together in a bowl. Beat unsalted butter and white sugar together in a separate bowl until creamy and smooth; add eggs, 1 at a time, beating well after each addition. Beat vanilla extract into the creamed butter mixture. Add flour mixture to creamed butter mixture; beat on low speed just until batter is combined, about 1 minute. Spread batter over nectarine layer.
- Increase oven temperature to 350 degrees F (180 degrees C).
- Bake in the preheated oven until cake is golden brown and a toothpick inserted in the center comes out clean, 35 to 40 minutes. Cool cake in pan on a wire rack for 15 minutes. Run a knife around edge of pan and invert cake onto a serving plate. Serve warm or at room temperature.