Season the salmon trimmings with the lemon juice and a generous grinding of black pepper.
Break the eggs into a bowl, season with a little salt and beat lightly with a fork. Add the salmon trimmings and pecorino to the egg mixture.
Warm a 20cm non-stick frying pan on a medium heat. Drop a knob of butter into the pan and when it starts to bubble after a few seconds, pour in the egg mixture.
Let the eggs bubble for a few seconds then gently draw the mixture in from the sides with a wooden spatula. Do this a few times so the setting mixture gathers in folds in the centre. Leave for a couple of minutes until the middle is almost set.
Grip the handle, tilt the pan down and away from you and let the omelette gather to the edge. Fold okthe nearest side over by a third with your spatula then fold it again.
Slide the omelette on to a plate and serve immediately.