Bring a large pot of heavily salted water to a boil. Add the spaghetti and cook according to the package directions.
While the spaghetti cooks, make the sauce. Heat a large skillet over medium-high heat. Add the olive oil and garlic, cook for 30 seconds, stirring. Add the anchovies and cook, smashing them with the back of spoon until dissolved. Add the capers, olives, oregano, red pepper flakes, and tomatoes. Stir to combine. Add the tuna and cook until the liquid has reduced by half, about 10 minutes.
Reserve ½ cup of the starchy pasta water and drain the pasta. Add the pasta to the pan, toss with the sauce until coated. Add the pasta water and cook for another minute. Add the arugula and nutritional yeast and cook for another minute or two or until the arugula is wilted, stir in the basil and serve.