Boil the prawns in shell and peel.
Cut lettuce leaves.
Put the chopped salad on a flat plate. Sprinkle with boiled shrimp. Pour over the sauce.
Prepare the sauce: in a cup, mix sour cream, mayonnaise, and ketchup and squeezed garlic. Add ketchup until the sauce becomes a pleasant pink color.
Garnish with tomato slices. Serve chilled.