For the tomato sauce, wash, clean and coarsely dice the tomatoes. Peel and chop the onion and garlic
Heat 1 tablespoon of oil in a saucepan and sauté the onions and garlic briefly until translucent. Add tomatoes and tomato paste. Season with salt, pepper and sugar. Bring to the boil and simmer in a closed pot for about 20 minutes
Finely puree the sauce and pass through a sieve. Bring to the boil again and simmer for about 1 hour until thick. Wash the basil, shake dry, pluck the leaves from the stalks and chop finely. Season sauce with salt, pepper and basil, except for a little bit for sprinkling.
Prepare the pasta in boiling salted water according to the instructions on the packet
Peel and finely dice the red onion. Heat 1 tablespoon of oil and fry the diced onion for about 5 minutes. Drain tuna and sardines and let them drain. Add the tuna, sardines and tomato sauce and bring to the boil
Parmesan cheese in shavings. Drain the pasta and collect approx. 5 tbsp. of cooking water. Put the pasta back into the pot. Add the sauce and turn the pasta in it. Serve and sprinkle with basil and parmesan