1) In a large bowl, combine the flour, cornmeal, xanthan gum, salt, and baking powder, and set aside.
2) In the bowl of your electric mixer, stir together the lukewarm water, oil, and instant yeast.
3) Add the dry ingredients all at once. First stir to combine, then beat at high speed for about 2 minutes, until the mixture is lightened, aerated, and resembles very thick cake batter.
4) Let the dough rise, covered, in a warm place for about 1 1/2 hours. It will become puffy and expand some, but won't double in volume. Towards the end of the rising time, preheat your oven to 400°F.
5) Divide the dough in half. Spread each half onto a well-oiled 14" pizza pan, or one 14" round and one sheet pan (an oiled offset spatula works well for this), and allow the crusts to rest for about 15 to 20 minutes.
6) Bake the crusts for 15 minutes, or until they're set and just starting to take on some color around the edges.
7) After topping with the chili and cheese, bake for an additional 15 minutes, or until the cheese is bubbly and beginning to brown. Remove from the oven, and garnish with scallions or chives, if desired. Allow the pizzas to rest for 5 to 10 minutes before cutting.
Yield: two 14" pizzas.