Whisk the chickpea flour, nutritional yeast, turmeric and salt, then whisk in the water a little at a time until smooth and lump-free. Rest the batter for 10 minutes.
Dice the red pepper, slice the mushrooms and crumble the tofu.
Heat half the oil in a 25 cm (10 inch) non-stick skillet over medium heat. Cook the pepper, mushrooms and tofu, stirring, for 5 minutes, then stir in the spinach to wilt. Tip into a bowl.
Wipe the pan, add half the remaining oil and heat over medium heat until shimmering.
Pour in half the batter and swirl to cover the pan. Cook for about 3 minutes, until the top looks dry and the edges lift, then flip and cook 1 minute more.
Spoon half the vegetables over one side, fold the omelette over and slide onto a plate. Repeat with the rest of the oil, batter and filling.
Serve hot with salsa. Chickpea flour must be fully cooked, so make sure the centre is set and not gummy.