Peel and finely slice the onion and press the garlic. Bring a pot of salted water to a boil. Meanwhile, heat a drizzle of olive oil in a pan and sauté the onion over low heat until it becomes translucent but not colored.

Add the tomato sauce, tuna, salt, and pepper, mix well, and let it simmer while the pasta cooks (which you should have added to the boiling water at the same time). Garnish with olives or cheese as you like. Drain the pasta, coat it with the sauce, and serve immediately!