(adapted from Gourmet, June 2009)
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 tablespoon sugar, divided
1/2 teaspoon pure vanilla extract
1 large egg
Zest of 1 large lemon
1/2 cup well-shaken buttermilk
1 cup fresh raspberries (about 5 ounces)
Preheat oven to 400°F with rack in middle. Butter and flour a 9-inch round or square cake pan.
In small bowl whisk together flour, baking powder, baking soda, and salt. Set aside.
In liquid measuring cup combine buttermilk, vanilla and lemon zest. Set aside.
In bowl of electric mixer beat together butter and 2/3 cup sugar at medium-high speed until pale and fluffy, about 2 minutes.
Add egg and beat well.
At low speed, mix in flour mixture in 3 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 tablespoon sugar.
Bake until cake is golden and a wooden pick inserted into center comes out clean, 25 to 30 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.