Rinse the squid, pat dry, cut the arms from the bodies and dice the arms into small cubes.
Rinse the peppers, cut in half, remove seeds and finely chop.
Rinse and dice the zucchini.
Blanch the tomatoes in hot water, peel, cut in half, remove the pulp and chop.
Mix together the peppers, zucchini, squid arms, onion and garlic in a bowl. Season with olive oil, salt and pepper. Fill into the squid bodies and seal with toothpicks. Season the outside with salt and pepper.
Spread the tomatoes in a baking dish, sprinkle with lemon juice and season with sugar, salt and pepper. Put the squid bodies on top and braise in a preheated oven at 180°C (approximately 350°F) for about 20-25 minutes.
Serve the squid sliced on the tomatoes, garnished with basil.