Heat the olive oil in a pan. Avoid the tuna and roast the tomato paste. Deglaze with water and stir until the tomato paste dissolves and the sauce is thick.
At the moment, cook the spaghetti in salted water as usual, drain and drain. Add olives and capers to the sauce and season with salt and pepper. Pour the sauce over the spaghetti and serve with grated parmesan.