Add the eggs to a saucepan and fill it with cold water. Bring water to a boil and once the boiling point is reached, boil eggs for 8 minutes (it's helpful to set a timer).
Prep ingredients per the instructions above.
Take the eggs out of the water and run them under cold water to cool them.
Peel the eggs, chop, and add them to a bowl. Mix in mayo as needed for a creamy consistency and season with dill, and salt and pepper to taste.
Lightly toast the bread.
Layer the bread with spinach, tomato, egg salad, and onion.
Mix together the sparkling water and lemon. Serve over ice if desired.
Serve: Cut the sandwich in half and enjoy with pickles, chips, and spritzer.