In a mixing bowl, add Red Onion (4 tablespoon), Celery (1/4 cup), Mayonnaise (2/3 cup), Garlic Powder (1 teaspoon), Salt and Pepper (to taste), and Lemon Juice (1 tablespoon). Mix until all combined.
Prepare hard-boiled Egg (2). Place the eggs in a single layer at the bottom of the pot and cover with cold water by an inch. Bring to a boil over medium-high heat. Turn off the heat, cover, and let sit for 8 to 10 minutes. Drain the water, cool the eggs in ice water and peel.
Add the Canned Tuna Packed in Water (14 ounce) and roughly chopped hard-boiled eggs and stir.
Cover the bowl with plastic wrap and place it in the fridge for 10-20 minutes.
Spoon tuna mixture onto Sandwich Bread (2 piece). Add any other desired toppings. Serve and enjoy!