Put the olive oil into a medium-sized casserole at medium heat. Smoke the onion until it gets a sweet light brown colour. It will take appr. 2-3 min.
Remove the water from the tuna chunks and empty them into the casserole. Mix the mixture well and leave it to boil for 3 min. Keep stirring it, to avoid getting stuck on the bottom of the casserole.
Add the tomato passata, the salt, the pepper, and the garlic gloves. Stir all the ingredients well until the mixture is unified.
Add 500ml water and the ground cinnamon powder and stir it well until it gets a homogeneous mixture.
Boil the mixture for 40 min. If you want a thick tuna sauce, boil the sauce for 5 more minutes.
Remove the casserole from the heat and let it rest.
Serve it with spaghetti, conchiglie shells, or linguine.
Preparation of the pasta.
Start boiling the pasta while your tuna sauce is in the cooking process, to serve it immediately.
Put water into a large casserole and bring it to a boil.
Add salt to the water.
Add the pasta to the boiling water and stir it to avoid sticking together.
Cook 10-12 min so that pasta is al dente.
Drain the pasta in a colander and put it back into the casserole.