Preheat oven to 350°. Lightly spray a wire rack with cooking spray; place rack in a foil-lined, rimmed baking sheet.
Place bacon on prepared rack; sprinkle with brown sugar.
Bake until sugar is melted and bacon is crispy, about 15 minutes. Remove from rack.
In a medium bowl, stir together sirloin, chopped pickles, salt, and pepper until combined. Divide mixture into 12 portions, and shape each portion into a 5-inch patty. Place 2 tablespoons pimiento cheese in center of 6 patties. Top with remaining patties, and press edges to seal. Refrigerate for 20 minutes.
Heat a large cast-iron skillet over medium heat. Cook for 4 to 5 minutes per side, covering during last 3 minutes of cooking.
Layer bottom half of rolls with lettuce, patties, tomato, pimiento cheese, and bacon. Garnish with pickles, if desired. Serve immediately.
Recipe by Southern Cast Iron at https://southerncastiron.com/pimiento-cheese-stuffed-burgers/