Cut zucchini into cubes or thin slices. The 3 tbsp olive oil saute the crushed garlic and chopped onion. Add peeled and diced tomatoes. Strain the sauce of tuna. Add to the tomatoes and let the sauce to thicken for 10-15 minutes. Season with salt, pepper and chopped dill. Boil zucchini steam or blanch in salted water for 5 minutes. Strain and still warm pour the warm sauce. Garnish with pieces of tuna and season with olive oil, lemon juice, chopped dill and onion.