05Remove vanilla pod from butter and stir butter into egg-sugar batter. Combine 1/2 cup flour and baking powder, then stir it into batter alternately with milk. Stir in apples, coating every piece with batter. Pour batter into pan, using fingers to pat top evenly.
06Bake for 25 minutes, then rotate pan; bake for about 25 minutes more, until cake pulls away from pan and is brown on top; a thin-bladed knife inserted into center will come out clean when it is done. Cool 30 minutes, then cut lengthwise and sprinkle slices with powdered sugar.