This is another straight-from-the-pantry dish for days when there’s no time to cook. My mother relied on it very heavily when I was growing up, and everyone loved it. The lemon zest wakes up all the flavors and perfumes the dish, but you could use red pepper flakes instead if you don’t have a lemon.
In a Large, heavy skillet, combine the marinara sauce, tuna, capers, and lemon zest. Simmer to blend the flavors, stirring and breaking the tuna into chunks, about 5 minutes. Stir in the parsley and ½ teaspoon each of salt and pepper. Season the sauce with more salt and pepper to taste.
To serve with pasta: Add drained freshly cooked pasta to the sauce, and toss to coat. Add enough reserved cooking liquid from the pasta to moisten.