Simply mix and combine everything together in a bowl, adjusting the texture and taste with more or less mustard and mayonnaise. Season with black pepper only, the canned tuna being salted already.
2 cans, 3 tsp homemade mayonnaise, 2 tsp pickle relish, 2 tsp mustard, 2 celery stalks, ½ cup onion, Freshly ground black pepper to taste