Let the peas thaw briefly. Drain the tuna and let it drip off on kitchen paper if necessary. Pluck into small pieces with two forks. Peel and chop onion
Heat the fat in a large pan. Sauté the onion in it until transparent. Beat the eggs until smooth, but not so frothy. Season with salt and pepper.
Pour the eggs into the pan. Spread peas and tuna fish on top. Let it simmer at low heat for about 10 minutes without lid, then about 5 minutes with lid
In the meantime, wash and clean the tomato, remove seeds if necessary and cut into cubes. Sprinkle the omelette with it and garnish with parsley if necessary. Tastes good with farmhouse bread