Cook the shells in a pot of salted boiling water until al dente.
While the pasta is cooking, finely chop the parsley and open the tuna. Once the pasta is cooked, drain and return it to the pot and mix it with the chopped parsley, tuna, and olive oil.
Before serving, garnish with lemon zest and juice and black pepper and flaky sea salt. Level the dish up with olives, capers, pesto, or cherry tomatoes.