Pearl Onion Tomato Salad

Make sure to make this with some decent tomatoes. Cut into cubes, add some halved pearl onions, preferably marinated in balsamic vinegar. Seeded black olives, some fresh basil.
A small chopped shallot, nevertheless.
For dressing, combine some of the onion marinade if nice, lemon juice, olive oil, salt and coarse black pepper.