This is the dish to cook when you don't really feel like cooking. It involves minimal swelter in the kitchen and almost no prep. If you can't find jarred tuna, substitute canned.
Bring a large pot of water to a boil. Cook pasta according to package instructions until al dente. Drain.
Gently toss pasta with peperoncini, arugula, tuna, parsley, 2 tablespoons oil, and some pepper in a large bowl. (Do not break up tuna too much.) Drizzle with remaining 2 tablespoons oil.