Preheat the broiler. Sift the garbanzo bean flour with the salt into a medium bowl. Slowly add 1/4 cup of the water, whisking constantly to form a paste. Beat with a wooden spoon until smooth. Whisk in the remaining water and let the batter rest at room temperature for 30 minutes. Stir in the rosemary and thyme.
Heat 1 tablespoon of the olive oil in a 12-inch nonstick ovenproof skillet. Add the garlic and sauté for 30 seconds. Stir the batter once, pour it into the skillet and drizzle the remaining 2 tablespoons of olive oil on top. Cook the pizza over moderately high heat until the bottom is golden and crisp and the top is almost set, 2 to 3 minutes. Burst any large air bubbles with the tip of a knife.
Sprinkle the tomato, onion, parmesan and pepper over the top. Place the skillet under the broiler and cook until the pizza is golden and crisp, 4 to 5 minutes. Slide the pizza onto a work surface, cut into wedges and serve hot. Garnish with fresh basil.