Pasta with Tuna Sauce

From allrecipes.com
I usually have most of these ingredients on hand (except capers, but I'd just omit them), so this would make a quick lunch when we don't have any leftovers.

1 tablespoon olive oil
1 onion, chopped
2 cloves crushed garlic
1 tablespoon capers
1 (14.5 ounce) can crushed tomatoes
1 tablespoon lemon juice
1 tablespoon chopped fresh parsley
1/4 teaspoon red pepper flakes
2 (6 ounce) cans tuna, drained
1 (16 ounce) package dry pasta

1.In a large saute pan, heat oil over low heat. Add onion and garlic; cook and stir until onion is tender. Stir in capers, tomatoes, lemon juice, and parsley. Season with red pepper flakes to taste. Simmer gently for 3 minutes to thicken sauce. Fold in tuna, and heat through.
2.While sauce is cooking, add pasta to a large pot of rapidly boiling water; cook till just tender. Drain well.
3.Toss pasta with sauce, and serve.