Tuna Fish Salad

1 large red onion, finely chopped
1 cup finely chopped celery
1 4-ounce jar of small capers, well-drained
4 cans of wild-caught skipjack tuna, well-drained tuna
1 teaspoon black pepper
1 lemon
1 cup pure avocado mayonnaise
Romaine lettuce

Mix finely chopped onion, finely chopped celery, well-drained capers, well-drained tuna, and black pepper in a large bowl. Zest the peel of one lemon and add to bowl. Juice the lemon and add to bowl. Stir in one cup of pure avocado mayonnaise. Chill for one hour and serve on a bed of Romaine lettuce.