Prepare the Tuna: Drain the canned tuna thoroughly (if you’re using tuna packed in oil, feel free to save a tablespoon of oil for extra flavor). Break the tuna into chunks using a fork.

Chop the Vegetables: Finely chop the celery, red onion, and any other vegetables you want to add.

Mix the Dressing: In a small bowl, whisk together the mayonnaise, Dijon mustard, lemon juice, salt, and pepper.

Combine Ingredients: In a large mixing bowl, combine the tuna with the chopped vegetables. Pour the dressing over the mixture and gently stir until everything is evenly coated.

Serve: Spoon the tuna salad onto lettuce leaves for a light lunch, or use it as a sandwich filling between slices of your favorite bread. You can also serve it on crackers as a snack or appetizer.