Whisk chickpea flour, salt, pepper, and cumin together in a bowl. Add warm water gradually, whisking to prevent lumps. Add 2 tablespoons olive oil and whisk until completely smooth. Cover and rest at room temperature for at least 30 minutes — up to 1 hour for best results.
Set oven to broil. Place a 10–12 inch cast iron skillet inside and heat for at least 10 minutes until very hot.
Remove the hot pan carefully using oven mitts. Add remaining 1 tablespoon of olive oil and swirl to coat — it will smoke slightly. Pour the rested batter into the center and tilt the pan to spread evenly. The batter should sizzle on contact.
Slide immediately back under the broiler. Cook 5–8 minutes until the top is golden with darker charred spots and the edges have pulled away from the sides of the pan. The center should look set, not wet.
Rest 2 minutes in the pan. Slide onto a cutting board. Scatter flaky salt, fresh rosemary, and red pepper flakes over the surface while still hot. Cut into wedges with a sharp knife or pizza cutter. Serve immediately.
