Slice the bitter melon vertically, remove the seeds and slice thinly. Rub with some salt (not listed). Boil water in a pot, add the bitter melon and when it comes to a boil, remove and drain. Soak in water, then squeeze out.

Thinly slice an onion and soak in water for about 10 minutes. Drain and squeeze out the water with your hands.

In a bowl, combine the bitter melon, onion, and tuna flakes and add mayonnaise and lemon juice. Taste, and add salt and pepper if necessary.