Drain and flake 1 can (5–6 oz) tuna
Finely chop 1/4 cup celery (optional)
Finely chop 1/4 cup red onion (optional)
Chop 1–2 tablespoons pickles or relish (optional)
Add 2–3 tablespoons mayonnaise
Add 1 teaspoon Dijon mustard (optional)
Add 1 teaspoon lemon juice or vinegar
Add 1/2 teaspoon salt (to taste)
Add 1/4 teaspoon black pepper (to taste)
Stir until evenly mixed
Taste and adjust seasoning and mayo as needed
Serve on bread, crackers, or greens