Drain tuna in a fine-mesh sieve for 2 minutes. Press gently with the back of a spoon to remove excess liquid. Pat dry with a paper towel if still wet.
2 cans tuna
Dice celery into ⅛-inch pieces. Cut red onion into the same size. Soak onion in ice water for 5 minutes if you want a milder flavor, then drain and pat dry.
2 ribs celery, ¼ cup red onion
In a medium bowl, mix tuna, celery, red onion, mayonnaise, lemon juice, and mustard. Stir until mayonnaise coats all ingredients evenly. Add capers if using.
2 cans tuna, 2 ribs celery, ¼ cup red onion, ⅓ cup mayonnaise, 2 tablespoons lemon juice, 1 teaspoon mustard, 1 tablespoon capers
Taste and adjust seasoning with salt, black pepper, and more lemon juice as desired. The salad should taste bright but balanced without sharpness.
Fold in fresh dill gently to distribute it without bruising the leaves. Cover and chill the salad for 30 minutes before serving for the best flavor meld.
2 tablespoons fresh dill
