Combine 1/3 cup water in a large bowl with chickpea flour, cornstarch, 1 tablespoon olive oil, garlic powder, and 1/2 teaspoon kosher salt.
Mix well with a spatula, it should hold together well to form a ball and be only slightly sticky. If too sticky, add a little more flour.
Flour your hands and roll it into a ball. Divide the mixture in 4 portions and form 4 balls.
Put breadcrumbs into a large shallow bowl, place a ball on top and press with your fingers adding some crumbs on top so your fingers don’t stick to form a thin cutlet about 1/4 inch thin. Flip to cover both sides with breadcrumbs.
Repeat with the remaining balls.
Heat 2 tablespoons oil in a large skillet over medium heat. Cook the cutlets on both sides for about 2-3 minutes on each side, until golden.
Divide 1 1/2 cups arugula on each plate with 1/4 cup each of tomatoes and chickpeas seasoned with salt and pepper and serve over the cutlets, with plenty of lemon for squeezing.