In a bowl, mix your ketchup, salt, pepper and garlic into your ground beef. Don't over work it. Just enough to get everything evenly incorporated. Form your meat into 8 patties, and let rest for about 10 minutes to bring them up to room temp.
While your ground beef are coming up to room, mix ketchup, mayo and dill relish together to make your secret sauce. Store in the fridge until ready to use.
Grill your burgers over medium heat for about 7 minutes, then flip and add cheese. Continue cooking for about another 5-7 minutes until the center temp is about 135-140F for medium. Add sourdough onto the grill to toast.
Assemble burger with spread, burger, lettuce, tomato, and even some guacamole. Enjoy!