Heat a pot over water over high heat until boiling.
While the water is heating, prep vegetables per instruction above.
Cook the chicken: When the water is hot, add the chicken and cook at a simmer for about 10 minutes until the chicken has reached an internal temperature of 160°F. Remove from water and transfer to the fridge to cool.
In a medium bowl, mix the minced onion, celery, dill, and mayo and reserve in the fridge.
Once the chicken is cool, dice into small, bitesized pieces and place back in the fridge to cool fully.
Make the chicken salad: Once cooled, add the chicken to the mayo mixture. Season with salt and pepper to taste.
Serve: Spoon the chicken salad onto the lettuce, top with onion and tomato. Enjoy with carrots, ranch, and sparkling water.