Put the tofu, garlic, nutritional yeast, oil, cumin, and salt in a food processor and blend the mixture until smooth.
Add the flour and cornstarch and pulse to combine.
Place a large non-stick skillet over medium-high heat and lightly coat with cooking spray.
Pour 1/2 cup of the mixture into the skillet, moving it around so that it spreads out evenly.
Cook for 3 to 5 minutes until the top of the omelet is dry to the touch. Flip and cook for a further minute, to cook the other side.
Transfer the omelet to a plate and repeat with the remaining mixture.
In a separate small skillet, heat some oil over medium heat. Add the onion and mushrooms and cook for 3 minutes until the onion is translucent. Stir in the spinach and cook for a further couple of minutes, until the spinach has wilted.
Divide the spinach, onion, and mushroom topping over the two omelets and serve hot.