This batter is a cinch to whip up. Mix it, dump it in your cake pan (I used a 9 inch springform pan) and then scatter a cup of raspberries over the top. Sprinkle with sugar and pop it in the oven for 25 minutes.
Whisk together flour, baking powder, baking soda, and salt.
Beat together butter and sugar about 2 minutes, then beat in vanilla and egg.
Slowly mix in flour mixture in 3 batches, alternating with buttermilk, beginning and ending with flour. Mix just until combined.
Pour batter into cake pan and smooth top. Scatter raspberries over the batter and sprinkle with reserved sugar.
Bake until cake is golden brown, about 25-30 minutes. Cool in pan for 10 minutes and then invert onto a cooling rack to cool for 15 minutes more before serving.