How to Make It
Preheat the broiler. Sift the chickpea 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 3/4 cup of water and let the batter stand at room temperature for 30 minutes, then stir in the rosemary.
Heat 1 tablespoon of the olive oil in a 12-inch nonstick ovenproof skillet. 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, then 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.
Chickpea flour is available at Indian and Middle Eastern markets, at health-food stores and by mail from (800-352-3451).