Finely dice the 1 red onion, cut the 200 g guanciale into small strips, and cut the 400 g fresh blast-chilled tuna into 2 cm cubes.

Bring a large pot of generously salted water to a rolling boil over high heat.

Heat 1 tbsp extra virgin olive oil in a large skillet over medium heat. Cook the 200 g guanciale until its fat renders and the strips are crisp, about 5 minutes.

Add the diced red onion to the rendered guanciale fat. Sauté until softened and translucent, about 4 minutes.

Add the 400 ml tomato passata to the skillet and season with salt and black pepper. Simmer the sauce gently for 10 minutes.

Add the 300 g spaghetti to the boiling water. Cook until 2 minutes shy of the package al dente time.

Reserve 120 ml pasta cooking water, then drain the spaghetti well. Keep the pasta warm while the tuna cooks.

Add the 400 g tuna cubes to the simmering tomato sauce. Cook gently for 2 to 3 minutes, leaving the tuna moist and just cooked through.

Add the drained spaghetti to the skillet. Toss with up to 120 ml reserved pasta cooking water until the sauce coats the pasta.

Tear in the fresh basil and toss once more. Serve immediately topped with grated Pecorino Romano cheese and extra black pepper.