The amount of tuna given here equals half of a typical can of Italian tuna (about 150 grams or 5 ounces); use the other half for a sandwich or salad. The important thing is that the tuna be preserved in olive oil.
This recipe is one of Judith Jones' meals for one.
Meanwhile, heat olive oil in a medium skillet over medium-low heat; sauté onion or shallot 3 to 4 minutes, until limp. Add garlic and tomatoes and sauté for another minute. Splash in wine and cook down, about 4 minutes. Break up tuna, dropping chunky flakes into the pan. Stir in olives. Add at least 1/4 cup pasta water to the sauce. When pasta is al dente (taste to be sure), use a big strainer-like spoon to transfer it to the pan. Stir to combine, and cook for a minute. Add salt to taste if needed and more pasta water if sauce is too dry. Spoon pasta with sauce into a bowl, and scatter parsley on top.
Adapted from The Pleasures of Cooking for One, by Judith Jones, copyright © 2009, with permission from the publisher, Alfred A. Knopf, a division of Random House, Inc.