Macerate the Onions: In a small bowl, combine the chopped red onion with approximately 1 tablespoon of the fresh lemon juice. Stir to coat and set aside for at least 10 minutes while you prepare the other ingredients. This step helps to soften the onion's pungent flavor.

Form the Salad Base: Lightly drain the olive oil from the canned tuna (you may reserve a bit of this flavorful oil if you prefer a richer salad). Flake the tuna into a spacious mixing bowl. Add the rinsed and drained white beans to the bowl. Gently fold the tuna and beans together, taking care not to mash the beans excessively.

Incorporate Flavor Elements: To the tuna and bean mixture, add the macerated red onions (including any lemon juice from their bowl), the chopped Kalamata olives, fresh parsley, the remaining lemon juice, lemon zest, red chili flakes, and freshly ground black pepper. Stir gently but thoroughly until all components are well distributed.

Adjust Seasoning and Consistency: Taste the salad. If you desire a brighter, more acidic note, incorporate a little more fresh lemon juice. If the salad seems somewhat dry for your liking, drizzle in a small quantity of extra virgin olive oil. Season with salt until the flavors are perfectly balanced to your preference.

Chill and Serve: For the best flavor melding, cover the salad tightly and refrigerate for at least 20-30 minutes before serving. This salad can be stored in an airtight container in the refrigerator for up to 3 days.