Bison Meatloaf Burger with Rosemary Ketchup

Name: Bison Meatloaf Burger with Rosemary Ketchup
Ingredients: 2 pounds ground bison; 1/2 cup chopped red onion; 1/4 cup breadcrumbs; 1/4 cup ketchup; 2 tablespoons chopped fresh parsley; 2 tablespoons Worcestershire sauce; 1 tablespoon chili powder; 1 tablespoon garlic powder; 1 large egg; Kosher salt and freshly ground black pepper; Four 1-inch cubes sharp Cheddar; Oil, for oiling grill grates; 4 pretzel buns; Shaved Brussels Slaw, recipe follows; Rosemary Ketchup, recipe follows; 2 cups Brussels sprouts; 1/4 cup granulated sugar; 2 tablespoons apple cider vinegar; 1 teaspoon red pepper flakes; Salt and pepper; 1/2 cup ketchup; 1/4 cup brown sugar; 2 tablespoons chopped fresh rosemary leaves; Salt and cracked pepper