Can yeast be used as a main ingredient?
I don't know that you'd want to make a full meal of it, but it sounds like you'd enjoy nutritional yeast. You can find it at any "health food store" type of grocery. It is deactivated, so you don't need to worry about it filling you up with CO2. The flavor is somewhat reminiscent of Parmesan cheese. Googling "nutritional yeast recipes" will give you plenty of ideas for what to do with it.