Preheat oven to 350 degrees. I used a 10-inch cast iron skillet. (If you don’t have a cast iron skillet, you can use a frying pan to saute the vegetables in. Then a baking dish or pan of a similar size to bake the dip in; make sure to grease it.)
Heat the skillet or frying pan to medium heat, add butter, when the butter sizzles with a sprinkle of water, then add celery and onion. Saute for about 2-4 minutes or until the onion is translucent. Add the garlic and saute for another 2 minutes. Take off the burner and set aside.
In a medium-sized bowl add cream cheese (which should be at room temp), sour cream, mayo, sugar, liquid smoke, cayenne pepper, and salt then mix with a handheld mixer. Mix on low to medium speed until combined and most or all lumps are gone, do not overwhip. Next, add ⅓ cup mozzarella, ⅓ cup gouda, ⅓ cup cheddar, sauteed veggies, and the drained tuna then stir with a spoon until combined.
Pour the mixture into the cast iron skillet (or greased baking pan). Bake for 15-20 minutes until the cheese is completely melted and the dip is bubbling. Then broil on low for 2-4 min until moderately browned on top. Let the dip rest for 5 to 10 min. Then add a sprinkling of lemon juice and dill on top.