Sweet relish, diced celery for crunch, mayo, Lemon juice, S&P...
...and Old Bay. Maybe some mustard.
Any leftovers get mixed with egg/panko/onion/bell into pan sauteed Tuna cakes. Btw..cooking the tuna changes the taste. Ig's turn their nose up at U tuna salad will eat the cakes.
"You don't eat it tonight.....you'll get it for breakfast!"