Preparation
Bring a large pot of salted water to boil, cook pasta according to the package directions. Drain pasta, reserving ½ cup of pasta water for use in the sauce.
Meanwhile, heat the olive oil in a large sauté pan over medium-high heat. Add sliced onions, crushed garlic, anchovies, and Tuscan Seasoning to the pan and cook for about 3 minutes. Add tomatoes (and juices), vinegar, tomato paste, and olives. Sauté for 6-8 minutes, crushing the tomatoes against the side of the pan with a wooden spoon.
Add the drained spaghetti to the pan and toss with sauce, thinning with reserved pasta water, as needed. Toss with capers and torn basil or parsley leaves and serve immediately topped with additional red pepper flakes and grated parmesan cheese, if desired.