Sautée the sausage and onion until the onion is translucent.
Add the cilantro to the pot, then the eggs. Stir until the eggs start to set up and then leave them to brown.
Gently lift one side of the omelet and tilt the pan so that the funny part of the eggs runs underneath the omelet.
Once the omelet is set, flip the omelet in the pan, sprinkle the cheese on top, and slide it off the pan to a plate. Allow the second half of the omelet to fold over the cheese to create the classic half-circle shape.