Wash the lettuce, shake dry and cut into pieces. Peel, halve and slice the onion. Clean and wash the peppers and cut into strips. Wash the cucumber, quarter it lengthways and cut into pieces. Season 2 tablespoons of lemon juice with salt and pepper. Stir in 3 tablespoons of oil. Mix the prepared salad ingredients and vinaigrette. Let the salad stand.
Mix together the ketchup, mayonnaise and 1 tablespoon lemon juice. Spice up. First turn the feta in egg, then in flour and finally in breadcrumbs. Heat 2 tablespoons of oil in a pan. Fry the feta schnitzel in it while turning until golden brown. Put the salad on the plate. Arrange the feta schnitzel on top. Serve with sauce.