This is an emergency 'quickie' meal in my home. When time is short and I want to get something nutritious and tasty on the table fast, this is the meal I inevitably turn to as it is made with store-cupboard staples and everyone loves it.
Heat the olive oil in a small saucepan and add the onion; saute onion until it is translucent, 2-3 minutes, then add tomatoes and garlic; season to taste with salt, pepper and red-pepper flakes and boil over medium heat for 10-12 minutes until thickened somewhat; add basil and simmer 2 more minutes; add tuna, turn off heat and allow to 'sit' (flavours will blend) for 5 minutes.
This makes a very thick, flavourful sauce (you can thin with a little boiling water or some of the pasta cooking water if it's too thick for your liking).
Distribute pasta amongst 4 plates and top with sauce; pass grated parmesan cheese at the table or, alternatively, toss pasta and sauce together, then serve, passing grated cheese.
Note: If you don't want your sauce to be as 'chunky', you can puree the tomatoes before using.