1. Combine 1/2 cup water, sugar, and yeast in a small bowl, stirring with a whisk. Let stand 5 minutes or until yeast mixture is bubbly.
2. Weigh or lightly spoon flours, potato starch, and flaxseed meal into dry measuring cups; level with a knife. Combine flours, potato starch, flaxseed meal, xanthan gum, and salt in a large bowl; beat with a mixer at medium speed until blended. Add yeast mixture, 1 tablespoon oil, egg whites, and egg; beat at low speed 1 minute or until combined. Increase speed to medium; beat 2 minutes.
3. Coat a baking sheet with 1 teaspoon oil. Scrape dough onto pan. Lightly coat hands with oil. Press dough into a 14-inch circle, coating hands with oil as needed to prevent dough from sticking. Coat top of dough with any remaining oil. Cover with plastic wrap, and let rise in a warm place (85°), free from drafts, for 30 minutes.
4. Preheat oven to 400°.
5. Remove plastic wrap, and bake crust at 400° for 17 minutes or until bottom lightly browns. Cool completely. Increase oven temperature to 425°.
6. Spread marinara over crust, leaving a 1/2-inch border; top with mozzarella cheese, pepperoni, and Parmesan cheese. Bake at 425° for 16 minutes or until crust is golden and cheese melts.