Preheat oven to 400°F.
Combine chickpea flour, nutritional yeast, baking powder, salt, and pepper in a bowl with 2½ cups water. Whisk to combine and set aside while preparing the veggies.
Heat olive oil over medium-high heat in a skillet.
Add all veggies to skillet (except for green onions) and cook until veggies cook down and begin to brown, about 7 minutes.
Add green onions to skillet and cook 2 minutes more. Season with salt and pepper to taste and remove from heat.
Brush a standard sized muffin tin and one smaller, 6 muffin tin with olive oil.
Divide veggie mixture between muffin cups by the heaping tablespoon.
Divide any remaining veggies between cups.
Using a ¼ cup measure, fill cups with chickpea batter.
Use a spoon to gently stir each cup to ensure the batter gets under the veggies.
Bake for 30 - 35 minutes, until a toothpick inserted in center comes out clean and frittatas are beginning to brown on top.
Remove from oven and allow to cool for 10 minutes (this allows the batter to set) before removing from tin and cooling on a rack.
Depending on your muffin tin, you may have to use a knife or offset spatula to gently loosen sides of frittatas before removing from tin.
Serve warm and enjoy!