Adapted from Gourmet, June 2009

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 (146 grams) 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 (see Note) raspberries evenly over top and sprinkle with remaining 1 1/2 Tbsp sugar.

Bake until cake is golden and a wooden pick inserted into center comes out clean, 25 to 30 minutes (but check in on it sooner, please. Because my oven is new and far from correctly calibrated, I can’t weigh in on the accuracy of this baking time.) Cool in pan 10 minutes, then turn out onto a rack and cool to warm, 10 to 15 minutes more. Invert onto a plate.