Peel the hard-boiled eggs and place them in a mixing bowl.
Mash the eggs with a fork to your desired consistency.
Add mayonnaise and Dijon mustard; mix well.
Stir in chopped dill, salt, and pepper.
Toast the slices of bread if desired.
Lay a leafy lettuce leaf on one slice of bread.
Scoop the egg salad mixture onto the lettuce.
Top with a slice of tomato.
Place the second slice of bread on top.
Cut the sandwich in half and serve immediately.