For the burger sauce: In a small bowl mix mayo, ketchup, mustard and pickle relish. Place in the fridge for later.
In a small bowl, mix ground turkey, ketchup, mustard, finely chopped onion, worcestershire sauce and minced garlic. Form four hamburger patties and sprinkle both sides with salt and pepper.
Heat your skillet to medium-high heat. Once the skillet it nice and hot, add the turkey burger patties and cook for about 4-5 minutes, undisturbed. Flip patties over and cook for an additional 3 minutes. Place a cheese slice on each patty and turn off heat. Cover and let cheese melt.
Butter the hamburger buns and heat a skillet to medium-high heat. Lay buns butter side down in skillet and cook until golden.
Top your buns with a turkey patty, burger sauce, avocado, lettuce, tomato, and red onion. Enjoy!