Place flour, cornmeal, baking powder and salt in a bowl.
In a stand mixer with the paddle attachment, add the butter and whip until soft.
Add the sugar and whip on medium speed until fully incorporated, about 2 minutes.
Add the vanilla and incorporate.
While on medium speed, add the eggs one at a time, completely combining in between each egg.
Add 1/3 of the dry ingredients, then 1/2 of the sour cream, then another 1/3 of the dry ingredients, then the sour cream, then the last of the dry ingredients.
Place in a buttered and floured loaf pan (9x5x3-in.) and bake in a 350°F/180°C oven for 50 - 55 minutes or until a cake tester comes out clean.
Cool for 10 minutes on a nonstick bakeware rack and then remove from pan. (Run a knife around the edges to release if necessary.) Cool completely.