Whisk together chickpea flour and water and allow to rest, refrigerated, for a minimum of one hour and up to overnight.
Preheat oven to 450 F (230 C).
Heat 1 tablespoon (15 mL) of olive oil over medium-high heat, add the onions and peppers, and sauté for two to three minutes, until soft. Add the garlic and season with salt and pepper, cook for one minute, then transfer the veggies to a plate.
Wipe out the pan and return to the heat, add the remaining olive oil.
When the oil is shimmering, carefully add the batter, taking care to avoid any sputtering oil.
Add the cooked veggies to the pan with the batter, spreading evenly and pressing into the batter. Arrange the tomato and zucchini slices across the top in a circular pattern, then sprinkle with the herbs, season with salt and pepper.
Transfer the hot pan to the oven and bake for 10-12 minutes until the batter is cooked, the top is brown and bubbly, and the sides are starting to crisp up and pull away.
When the socca is ready, slice into wedges and serve warm.