Lusty Pasta with Sardines

Name: Lusty Pasta with Sardines
Ingredients: 1/2 large onion, diced medium fine; 2 garlic cloves, coarsely minced; 1 tin of sardines in oil, larger bones removed; 1 tablespoon capers in brine, drained; 28 ounces can of tomatoes, pureed or whole (not diced); 2/3 cup flat-leaf parsley, coarsely chopped; 10 oil-cured black olives, pitted and roughly chopped (you can use other olives if you can't find oil-cured ones); 1/2 teaspoon oregano; olive oil; Red pepper flakes to taste; Salt and black pepper, to taste; 2/3 pound spaghetti or linguini; Zest of one lemon, juice of 1/2 lemon