Onion peel, halve and finely dice. Wash, clean and chop the tomatoes. Wash basil and shake dry. Peel the leaves and cut into strips. Dice the feta cheese.
Mix onion, tomatoes and basil. Whip vinegar and 1 tablespoon of oil and fold in. Season to taste with salt and pepper. Heat 2 tablespoons of oil in a frying pan. Add slices of bread and fry on both sides until golden brown.
Take out slices of bread and cut them in half. Spread the tomato and feta cheese mixture on the bread slices.