Lightly whisk the eggs in a bowl - they should be broken up but not frothy.
Finely chop the onion, tomato, chili and cilantro. Add them to the eggs, along with the turmeric and chili and stir to combine. Add a pinch of salt to taste, if you like.
Gently warm the oil in a small-medium skillet/frying pan over a medium heat (see notes) and add the egg mixture while it's still warming up.
Cook the omelette on the first side for around 2-4 minutes until it is cooked on the sides and largely cooked in the middle. Cover the top of the omelette with a small plate and flip it on to the plate and back into the skillet to turn. Cook on the other side for a minute or two to be gently brown and cooked through. Serve as it is or with roti/bread.
Notes
If you prefer the onion to be slightly sweeter tasting, you can pre-cook them a minute or two, or else make sure you cut them really finely. I used an 8in/20cm skillet/frying pan but slightly larger eg 10in/25cm would allow you to get a thinner omelette.This is a great base of ingredients, but you can add others too eg some grated coconut, spinach or additional spices.