In a food processor, add corn flour, gluten-free flour blend, garlic powder and salt and pulse to combine.
Add water one tablespoon at a time and pulse until a dough forms. You may not need all of the water. You don't want the dough to be too wet but you should be able to form it into a ball with your hands.
Pat into a flat circle and chill for at least an hour.
Preheat oven to 375F. Line a baking sheet with parchment paper.
Roll out the dough to a 12-inch circle about ½ inch thick. Place tomatoes cut side up in the middle of the dough.
Crimp dough over the filling leaving a circle in the middle. Brush crust with oil and drizzle the remaining oil over the tomatoes.
Top with a sprinkle of salt and pepper over both the filling and the dough.
Bake at 375F for 40-50 minutes, until crust is golden brown.
Remove from the oven and sprinkle fresh basil over the top. Cut into 8 pieces and serve.