Bring a large pot of salted water to a boil. Once boiling, add penne pasta and cook until al dente, stirring occasionally.
In the meantime, prepare the sauce. In a frying pan, add olive oil, tuna and minced garlic. Toss for 2 to 3 minutes, breaking the larger chunks of tuna with the help of a wooden spoon.
Add the peas, stir and wait for another 2 minutes.
Finally, add tomato purée, and season with salt and pepper.
Cook on medium-low for 10 minutes. If the sauce becomes too dry, you can add one or two tablespoons of pasta water.
When the pasta is ready, drain it and pour it in the pan with the sauce. Toss on medium heat for 30 seconds.