1. Preheat oven to 400°.
2. Weigh or lightly spoon white rice flour, potato starch, and tapioca flour into dry measuring cups; level with a knife. Combine white rice flour, potato starch, tapioca flour, xanthan gum, baking powder, and salt in a medium bowl, stirring with a whisk.
3. Combine 1 cup water and butter in a medium saucepan over medium-high heat; bring to a boil. Add flour mixture, stirring well with a wooden spoon until mixture is smooth and pulls away from sides of pan. Remove from heat; place dough in the bowl of a stand mixer fitted with a paddle attachment; beat at medium-high speed 1 minute. Add eggs, 1 at a time, beating well after each addition. Scrape dough off sides of bowl using a rubber spatula; beat 1 minute or until dough is smooth (dough will be sticky).
4. Spoon 2 tablespoonfuls dough 2 inches apart onto a baking sheet lined with parchment paper. Bake at 400° for 15 minutes. Reduce oven temperature to 350°. Bake an additional 18 minutes or until tops are golden brown and puffs sound hollow when tapped. Remove from oven; cool completely on pan.
5. Cut top one-third of each puff horizontally using a serrated knife. Top bottom half of each puff 1 tablespoon whipped topping. Replace top half of each puff. Sprinkle with powdered sugar. Serve with fresh raspberries, if desired.