Stone black olives. Finely chop the olives. Peel garlic and press it through the garlic press to the olives. Stir in oil. Season with pepper. Toast the slices of bread.
Cut cheese into slices. Peel onions and cut into thin rings. Wash the lettuce leaves and dab dry. Place some lettuce leaves on each slice of bread, spread cheese and onion rings on top. Spread with the olive pesto, cover with a second slice of bread