Heat the oil in a medium sized saucepan over medium low heat and sauté the garlic, chopped onions  just until the onions are soft, while stirring often for about 5 minutes.

Add in the chili flakes, passata, salt, and pepper and stir well.

Fill the bottle of passata three quarters of the way full with water. Give it a good swirl and add this to the sauce.

Bring the sauce to a boil then lower the heat, cover and simmer for about 45 minutes or until the sauce thickens.

While the sauce is slowly simmering, bring a large pot of water to boil. Salt the water and cook the pasta until al dente — tender but still with a little bite.

Add the drained tuna to the tomato sauce and allow to simmer for about 5 minutes.

When ready, drain the pasta and toss with some of the tomato sauce. Plate the pasta and top with more sauce and a sprinkle of chopped parsley.