Drain any liquid from the tofu package. Add the tofu, nutritional yeast, cornstarch, brown rice flour, unsweetened non-dairy milk, paprika, onion powder, turmeric and black salt (or regular salt) to a blender. Blend until smooth, scraping down the sides as needed. Set aside.
If you want to use sautéed vegetables as your filling, cook them now in a small pan with a little olive oil until soft, then set aside. You can even use the same pan you will make your omelette in, just place the cooked vegetables on a plate and keep them close by. Have any vegan cheese you will use nearby as well.
Make the Omelette: Add a few tablespoons of olive oil to a medium non-stick pan (or spray with oil) and turn to medium-high heat. Once hot, pour half of the omelette batter into the center of the pan, trying to make a circle. You can use a spatula to encourage it to spread, sort of like a pancake. You don't want it to be too thick, about 1/4-1/2 of an inch thick is perfect.
Cover and cook for 3-4 minutes, or until the top looks somewhat dry and set, no longer liquidy. At this point, if for some reason it was thicker than you thought or it's not cooked all the way through, you can carefully flip the omelette over and cook the other side for 1-2 minutes.
Add any fillings you want (I used cooked onions, mushrooms, spinach and daiya cheddar shreds) to one half of the omelette, then fold one side over to cover the fillings. Cover and cook for another 1-2 minutes, until the cheese has melted.
With a spatula, carefully transfer the omelette to a plate and serve with any additional toppings desired. Repeat with the rest of the batter and toppings. The recipe makes 2 omelettes. Enjoy!