Rinse and halve the tomatoes.
Rinse bell peppers, cut in half, remove seeds and cut into strips.
Cut olives in half.
Peel onion and dice.
Whisk together olive oil, vinegar and lemon juice and season with sugar, salt and pepper. Toss dressing with prepared ingredients, garlic and capers. Marinate for 10 minutes. Stir in basil, season to taste and serve in bowls.