This cake should not turn out gummy as long as you use a good quality gluten free 1 to 1 baking flour that incorporates xanthan gum in it’s ingredient list. I don’t recommend swapping the gluten free baking flour for any other gluten free flours such as rice flour, brown rice flour, tapioca flour, corn starch, almond flour, tapioca starch, potato starch, and so on, since this can result in a gummy, really unpleasant texture if the ratios aren’t perfect.