In a mixing bowl, combine the drained tuna, mayonnaise, Dijon mustard, chopped celery, chopped red onion, chopped parsley, and lemon juice.
Mix all the ingredients together until well combined. If you prefer a creamier texture, you can add more mayonnaise.
Season the tuna salad with salt and pepper to taste. Adjust the seasoning as needed.
If desired, add any optional add-ins like chopped pickles, capers, diced apples, or sliced grapes for extra flavor and texture.
Once everything is mixed together, cover the bowl and refrigerate the tuna salad for at least 30 minutes to allow the flavors to meld together.
After chilling, give the tuna salad a final stir and taste, adjusting the seasoning if necessary.
Serve the tuna salad on sandwiches, wraps, crackers, or over a bed of lettuce as a salad.
Enjoy your delicious and versatile Tuna Salad!