Bring a large pot of lightly salted water to a boil. Cook spaghetti in the boiling water, stirring occasionally, until tender yet firm to the bite, about 12 minutes. Drain, reserving 1/4 cup pasta water.
While pasta cooks, heat olive oil in a saute pan over medium heat. Once oil is shimmering, add onion, Kalamata olives, capers, anchovies, and garlic. Cook and stir until onions are soft, about 5 minutes. Add crushed tomatoes, white wine, and red pepper flakes. Stir to incorporate.
Nestle the tuna steaks into the sauce, cover, and cook until the tuna flakes easily, about 10 minutes. If sauce is too thick, add in the reserved pasta water, 1 tablespoon at a time. Add in the Italian seasoning.
Serve tuna and sauce on top of cooked pasta. Garnish with basil if desired.
Spicy Tuna Puttanesca · Dinner Match Lab | Dinner Match Lab