Separate the lettuce into leaves; wash and spin dry in a salad spinner. Alternatively, wash in a colander, then transfer to a clean towel and pat dry. Set aside.
2 heads butter (Boston) lettuce
Wash and dry the the remaining fresh produce.
2 red bell peppers
1 small bunch cilantro
Drain the tuna and transfer to a large salad bowl; flake with a fork.
4 (6 oz) cans chunk light tuna in water
Quarter the bell peppers lengthwise; remove and discard the stem, seeds, and membranes. Small dice the peppers (cut into ¼-inch cubes) and add to the salad bowl.
Halve the avocados lengthwise and twist the halves to separate, then remove the pit with a knife or spoon; scoop out and small dice the flesh (cut into ¼-inch cubes). Add to the salad bowl.
Using a knife, shave the cilantro leaves off the stems at a downward angle, working away from your body; discard the stems and finely chop the leaves. Add about ¾ of the cilantro to the salad bowl and save the rest for garnishing.
Trim off and discard the ends of the onion and remove the outer layer; small dice the onion (cut into ¼-inch pieces). Add to the salad bowl.
1 medium red onion
Juice the lime and add to the salad bowl.
Add mayonnaise, Dijon, salt, black pepper, and cayenne pepper to the salad bowl; mix the salad until thoroughly coated in the dressing.
6 tbsp mayonnaise
1 tbsp Dijon mustard
1 tsp salt
½ tsp black pepper
⅛ tsp cayenne pepper
To serve, make the lettuce wraps by spooning the tuna salad into the doubled up lettuce leaves, then garnishing with the remaining cilantro. Enjoy!