Finely chop the onion, thinly slice the celery stalk, finely dice the red pepper, and pit and slice the olives. Chop the fresh parsley. Having all vegetables prepped and ready will make assembling the salad mixture quick and efficient, and ensures even distribution of flavors throughout the tuna salad.

In a medium bowl, combine the drained tuna, mayonnaise, and yogurt, stirring gently to break up the tuna and create a creamy base. I like using Greek yogurt instead of all mayo because it keeps the salad lighter while still maintaining that rich, creamy texture. Add the black pepper and lemon juice, then fold in the prepared vegetables and parsley until everything is evenly combined. Taste and adjust seasoning as needed.

Lay out the lettuce leaves on a clean surface. Divide the tuna salad mixture evenly among the lettuce leaves, placing about 1/2 cup of filling in the center of each leaf. For easier wrapping, I like to keep the lettuce slightly cool—if they've been sitting out, give them a quick chill in the refrigerator for a few minutes so they're more pliable. Fold the sides of each lettuce leaf inward and then roll tightly from the bottom up to create a wrap, similar to a burrito.