Make green juice: Prep all of the juice ingredients per instructions above and place all of the ingredients into a blender. Blend until smooth.
Pour the green juice through a fine-mesh strainer into a storage container. Press on the solids with the back of a spoon to extract as much juice as possible. Discard the solids. Chill the juice before serving.
Prep ingredients for tuna sandwich per instruction above.
In a small mixing bowl break up the tuna with a fork. Toss with celery, lemon juice, and mayonnaise as needed until the tuna is to your desired creaminess. Season with pepper to taste. Stir to combine.
Lightly toast the bread in a toaster oven.
Assemble sandwich: Top toasted bread with lettuce, Tuna Salad, onion, and tomatoes.
Serve: Enjoy the sandwich with carrots, ranch dressing, and green juice