The original recipe wasn't very well drafted (they just lumped in all the ingredients in the list for all parts of the burger, and then for the sauce, unhelpfully stated "Make the special sauce. Combine all of the ingredients in a small bowl"). Hopefully I extracted the correct sauce ingredients.
1 cup paleo mayonnaise, such as Primal Kitchen brand
1/2 cup paleo ketchup, such as Primal Kitchen brand
1 tablespoon of sugar-free Dijon mustard
1 teaspoon chili powder
1 teaspoon garlic powder
1/4 cup sugar-free dill relish
2 tablespoons grated sweet Vidalia onion
1 tablespoon Valentina hot sauce (or to taste), or another sugar-free hot sauce
1 teaspoon kosher salt
freshly ground pepper