Finely dice the onion. Slice the zucchini and yellow bell peppers into bite-sized pieces. Slightly pierce the skin of the tomatoes in an 'X' shape at the bottom.

Bring a pot of water to a boil. Carefully place the pierced tomatoes in the boiling water for about 1 minute. Immediately transfer them to a bowl of ice-cold water.

Once cool enough to handle, peel the skin off the tomatoes. Cut the peeled tomatoes into small cubes.

Place a large pot or deep pan on the stove over medium heat. Add 1 tablespoon of butter and 1 tablespoon of olive oil.

Add the diced onion to the pot and cook, stirring occasionally, until it becomes translucent and softened, about 3 minutes.

Add the cubed tomatoes to the pot and cook for about 5 minutes, stirring frequently.

Pour in the tomato passata. Season the sauce generously with salt and black pepper to your liking. Add the sprigs of thyme and most of the fresh basil leaves (reserve some basil for garnish). Smash two garlic cloves with your knife and add them as well to the sauce.

Bring the sauce to a gentle simmer, then reduce the heat to low and let it simmer for 30 minutes, allowing the flavors to meld and the sauce to thicken slightly.

Add the sliced bell peppers and zucchini to the simmering sauce. Stir well and continue to cook for another 10 minutes, or until the vegetables are tender-crisp.

Drain the canned tuna and add it to the sauce along with the capers. Stir everything together gently and heat through for a couple of minutes.

While the sauce finishes, heat a separate large pan over medium-high heat. Add the remaining 2 tablespoons of butter.

Once the butter is melted and slightly bubbling, add the gnocchi in a single layer if possible (cook in batches if necessary). Cook the gnocchi for 5-10 minutes, flipping occasionally, until they are nicely browned and have a slightly crispy exterior.

Add the crispy gnocchi directly to the pot with the tomato tuna sauce. Stir gently to coat the gnocchi with the sauce.

Serve the dish immediately. Garnish each serving with fresh basil leaves that you reserved earlier.

Enjoy this super delicious Crispy Gnocchi with Tuna and Summer Vegetable Sauce. It's a wonderfully easy and satisfying meal!