Sift chickpea flour into a bowl; add salt, then slowly add the water, whisking to eliminate any lumps. Stir in 2 tbsp olive oil. Cover, and let sit for 1-2 hours.
The batter will thicken and should be about the consistency of heavy cream.
Preheat oven to 400°F.
Put a 9-inch cast iron skillet over medium high heat and add 2-3 tablespoons oil into heated pan, swirl to cover pan evenly. When the oil is hot add onion and let it cook for a few minutes. Pour in batter and sprinkle top with rosemary.
Drizzle a little olive oil over top and bake for 20-25 minutes until it is set in the middle and the edges are crispy.
Turn on broiler and broil top for a minute or two until it turns golden brown.
Allow to set for a few minutes and then carefully remove from pan.
Top with arugula, herbs, cherry tomatoes, a drizzle of olive oil, white balsamic and maldon salt. This recipe was inspired by Mark Bittman
