Preheat oven to 375 degrees. Mix together tuna, mayonnaise, celery, dill weed, garlic salt, and pepper in a medium sized bowl. Cut bagels in half and place on cookie sheet. Evenly distribute tuna mixture on each bagel. Bake in oven for approximately 15 minutes or until lightly brown. Place Havarti cheese on top of tuna and bake for another 3-5 minutes. Let bagels cool then garnish with dill weed, spinach, and tomatoes.
Recipe by The Gingham Apron at https://www.theginghamapron.com/tuna-bagel-bites/