Preheat the oven to 350°F. Line the wells of two 12 count cupcake pans with liners.
In a medium bowl use a whisk to sift together cake mix, cake flour, granulated sugar and salt. Sift together the dry ingredients.
In a separate bowl, mix together the sour cream, water and oil until combined.
Using a hand mixer gradually beat the wet ingredients into the dry ingredients.
After all of the wet ingredients are added continue mixing for around 2 minutes or until fully combined. (The batter will taste sweet at this point, but it will mellow as the cupcakes bake.)
Fill each muffin cup about 2/3 full. (Depending on how you separate the batter, you may be able to yield more than 24 cupcakes.)
Bake for 20 minutes until the tops are golden and a toothpick inserted into the center comes back clean. Cool completely on a wire rack.
Use a sharp knife to remove a small opening from the centers, and fill with fresh whipped cream, lime or lemon curd.
Garnish with fresh berries and a sprig of mint. Alternatively, serve glazed with a lemon or orange glaze.