Cook the spinach in some boiled water for 30 secs; drain it, and chop it. Mix the cheese and spring onion with the spinach in a bowl. In another bowl, whisk the eggs along with the hot sauce, salt, and pepper. Heat the oil in a skillet and spread it evenly in the entire surface. Add the eggs to it, and use a spatula to push the cooked portions towards the center. Tilt the skillet to let the uncooked egg fill in edges. Sprinkle the spinach and cheese mixture over the omelet, uniformly. Cook the omelet for 1 minute; check if the bottom is golden. Using the spatula, fold the omelet over the filling. Let it cook for 30 secs, and then slide it into a plate.