Rolls with herb frittata

Beat the eggs in a bowl, add a pinch of salt and some pepper and beat lightly with a fork.
Chop the herbs and add to the eggs.
Heat the olive oil in a non-stick frying pan, sauté the finely chopped onion, then add the egg mixture, cover and fry over a low heat until it sets, turn once.
Cut the frittata into four. Halve the rolls and immediately place some frittata inside each one. Close each roll and leave to rest for a short time. The bread will absorb the flavour of the warm frittata.
In the meantime, mix half of the mayonnaise with the diced cucumber and stir a tablespoon ketchup into the remaining mayonnaise.
Open the rolls again, carefully remove the frittata and spread the lower half of each roll with a tablespoonful of red sauce and cover with the remaining ingredients: a lettuce leaf, the frittata, tomato and the Emmentaler AOP slices. Spread the upper half of each roll with the cucumber mayonnaise mix and close the roll.