There is corn starch in traditional baking powder, and beside I think they charge to much. Here's my recipe.
I use Arm & Hammer baking soda. When I was first starting with this I used
vinegar as my acid. I am now using Mc Cormick or Frontier cream of tartar. 1 tsp baking
powder is basically 1/4 teaspoon baking soda to 1/2 teaspoon cream of tartar.
If you are using vinegar instead add about 1 teaspoon and just stir in at the
end of the recipe. I found I needed to add a bit of sugar to counter the
vinegar.