While we love many kinds of tuna salad, this classic version tops them all. The crispy celery and red onion add zest and crunch, while mayonnaise and a touch of mustard marry it all together. The lemon juice is optional as it’s not traditional, but we strongly recommend it to brighten up the flavors of the final dish.
Ensure tuna is very well drained to prevent a watery salad. Soaking the red onion in cold water is a critical step to mellow its pungent bite without losing the crunch; drain thoroughly afterward. Adjust the amount of mayonnaise and mustard to achieve your desired consistency and tang. Taste and adjust pepper and lemon juice (if using) just before serving. This salad is highly versatile and can be served on bread, lettuce leaves, or with crackers.