1 cup all-purpose flour
1/2 teaspoon baking powder
1/2 teaspoon baking soda
1/4 teaspoon salt
1/2 stick unsalted butter, softened
2/3 cup plus 1 1/2 tablespoons sugar, divided
1/2 teaspoon pure vanilla extract
1/2 teaspoon finely grated lemon zest (optional)
1 large egg
1/2 cup well-shaken buttermilk
1 cup fresh raspberries or other berries
Preheat oven to 400 F with rack in middle. Butter and flour a 9-inch round cake pan.
Whisk together flour, baking powder, baking soda, and salt and set aside. In a larger bowl, beat butter and 2/3 cup sugar with an electric mixer at medium-high speed until pale and fluffy, about two minutes, then beat in vanilla and zest, if using. Add egg and beat well.
At low speed, mix in flour mixture in three batches, alternating with buttermilk, beginning and ending with flour, and mixing until just combined. Spoon batter into cake pan, smoothing top. Scatter raspberries evenly over top and sprinkle with remaining 1 1/2 tablespoons sugar.
Bake until cake is golden and a wooden pick inserted into center comes out clean, 20 to 25 minutes. Cool in pan 10 minutes, then turn out onto a rack and cool to warm, 10 to 15 minutes more. Invert onto a plate.
Makes 1 thin 9-inch cake.
Make your own buttermilk: No need to buy buttermilk especially for this or any recipe. Add one teaspoon of vinegar or lemon juice to one cup of milk and let it sit until it clabbers, about 10 minutes. Voila, buttermilk!