Peel the onion and garlic clove, cut into small pieces. Mix with the minced meat, egg, breadcrumbs, thyme, marjoram, salt and pepper in a bowl. Form 6 small meatballs out of the minced meat and wrap each with 1 slice of bacon.
Fry the bacon meatballs in a hot pan with 2 tablespoons of oil and fry over medium to low heat for about 8 minutes.
In the meantime, wash the tomatoes and cut in half. Halve the melon, remove the seeds. Use a ball cutter to cut the melon into small balls. Season with salt, vinegar and chilli. Mix in 3 tablespoons of oil. Pluck the basil leaves from the stalks (save some leaves for decoration), roughly chop.
Drain the bacon meatballs on kitchen paper, serve with the lettuce and sour cream. Serve sprinkled with chilli.