In a mixing bowl, whisk together chickpea flour, water, nutritional yeast, turmeric, garlic powder, salt, and pepper until smooth, then let rest for 5 minutes.
Heat 1 tablespoon olive oil in a non-stick skillet over medium heat and sauté the onion for 2 minutes until softened.
Add chopped spinach to the skillet and cook for 1-2 minutes until wilted, then remove vegetables and set aside.
Add remaining oil to the pan, pour in half the batter, and tilt to spread evenly across the pan.
Cook for 3-4 minutes until edges lift easily, add half the vegetable mixture to one side, fold omelette in half, and cook for another minute.
Repeat with remaining batter and vegetables for the second omelette and serve warm.