While sliced strawberries stand, weigh or lightly spoon flours and potato starch into dry measuring cups; level with a knife. Combine flours, potato starch, remaining 1 tablespoon sugar, baking powder, and salt in a medium bowl; stir with a whisk. Combine coconut milk, vanilla, and eggs; stir with a whisk. Add to flour mixture, stirring with a whisk until smooth. Fold in diced strawberries.