Mix tuna, mayonnaise, mustard, celery, red onion, lemon juice, salt, and pepper in a bowl. Spread the mixture on bread slices.
Cook pasta according to package instructions. In a large bowl, combine tuna, cherry tomatoes, olives, red onion, olive oil, and vinegar.
Mix tuna, mayonnaise, mustard, celery, red onion, salt, and pepper in a bowl.Spread the mixture on bread slices.