Preheat oven to 350F. In a medium mixing bowl combine the yogurt, milk, vinegar, brown and white sugar, vanilla and oil and whisk ingredients well. Set aside.
In a large mixing bowl, combine the dry ingredients (flour, cornstarch, baking soda, baking powder, salt and spices) and whisk well.
While whisking the dry ingredients, slowly add the wet ingredients. Continue adding and stirring until the batter is combined and contains no lumps.
Grease and flour your pans (I used three 6" pans for this recipe) and pour the batter evenly into the pans and bake 25-30 minutes or until a toothpick comes out of the middle cleanly.
Let cakes cool in the pans for 10 minutes and then removed from pans and let cool completely. While your cakes are cooling, make the buttercream according to the instructions.
Once your cake is cooled, frost and decorate however you would like! Store in an airtight container for up to a week.