Preheat oven to 350F. Grease 3 (8-inch) cake pans. Sprinkle 2 tablespoons coarse sugar into the bottom of each pan. Shake the pan and turn to coat the entire pan bottom. Set aside.
In a large mixing bowl combine the butter and sugar. Using an electric mixer beat the mixture until light and fluffy. Add the eggs, one at a time, mixing just until the yolk disappears.
In a small bowl whisk together the flour, baking powder, baking soda and salt. Set aside.
In another small bowl, blend the sour cream, milk and vanilla together. Set aside.
Add 1/2 of the sour cream mixture to the sugar mixture and blend on low until incorporated. Next add 1/2 of the flour mixture and mix on low until blended. Scrape down the sides and bottom of the bowl as needed. Add the remaining sour cream and blend, then all the remaining flour. Blend on low just until incorporated. Scrape down the sides and bottom of the mixing bowl with a spatula and gently stir one more time.
Divide the batter equally between the three prepared 8-inch cake pans and bake until a toothpick inserted in the center comes out clean, about 20-25 minutes, rotating the pans after 15 minutes. Do not over bake!!! Cool in the pans for 10 minutes, then turn the cakes out and cool completely on a wire rack.