If you are baking your cake in the same size pans as the recipe recommends, the recipe will turn out fine. If you are trying to bake a larger version of your cake, you may need to reduce the doubled amount of baking powder, or your cake will not rise properly.

If you are more than doubling a recipe, it is best to weigh your ingredients instead of measuring with dry measures. When dealing with larger quantities, what is a slight variation in quantity becomes a large mistake. Also, if you are using dry spices, reduce the doubled amounts.