Bring a large pot of well-salted water to a boil, then cook the pasta according to the package directions until al dente.
Drain the pasta into a colander, rinse briefly with cold water to stop the cooking, and let it drain thoroughly.
In a large serving bowl, whisk together the extra virgin olive oil, lemon juice, lemon zest, minced garlic, sea salt, and black pepper until well combined.
Add the drained pasta, cannellini beans, cherry tomatoes, red onion, capers, chopped parsley, and rosemary to the bowl with the dressing.
Toss everything gently until the pasta and vegetables are evenly coated in the dressing.
Cover the bowl and let the salad rest in the refrigerator for 20 minutes before serving so the pasta absorbs the flavors.
Give the salad a gentle toss just before serving, and scatter the flaked tuna over top if you are using it.