Bring a large pot of heavily salted water to a boil. Once boiling add pasta and cook for 7-9 minutes or until al dente. Reserve 1 cup of the cooking liquid and drain pasta.

Heat oil over medium heat in a large frying pan. Add garlic and guajillos and fry for 30 seconds to a minute, don't let burn. Add pasta and reserved cooking liquid and toss to coat. Season with salt then add tuna, tomatoes, and parsley. Toss to combine and serve.