Creating delicious tuna salad sandwiches is straightforward. Follow these simple steps for the best results:

1. Prepare Tuna: Drain the cans of tuna and transfer the tuna into a medium mixing bowl.
2. Add Mayonnaise: Spoon the mayonnaise into the bowl with the tuna. You can adjust the amount based on your preference for creaminess.
3. Mix in Mustard: Add the Dijon mustard for an extra layer of flavor.
4. Incorporate Vegetables: Stir in the finely chopped celery and red onion. Feel free to add other veggies to your liking.
5. Season and Flavor: Squeeze in fresh lemon juice, and season with salt and pepper. Mix well until combined.
6. Fresh Herbs: If using, fold in the chopped parsley or dill for a fresh herbal touch.
7. Chill (Optional): For optimal flavor, let the mixture chill in the refrigerator for about 30 minutes.
8. Assemble Sandwiches: Spread a generous amount of the tuna salad on one slice of bread. Top with fresh lettuce and tomato slices before placing the other slice on top.
9. Serve or Store: Either serve immediately or wrap the sandwiches for later.

These steps ensure that your tuna salad sandwiches will be both tasty and satisfying.