Let's make it
Prepare outdoor grill for direct grilling over medium-high heat. In large skillet, melt 2 tablespoons butter over medium-low heat. Add onion and 2 tablespoons water; cover and cook 10 minutes, stirring occasionally. Uncover and cook 10 minutes or until very soft, stirring occasionally; add cola and cook 10 minutes or until golden brown, stirring occasionally. Makes about 1 cup.
In large bowl, gently mix ground chuck, salt and pepper; form into 4 (1/2-inch-thick) patties. Spray patties with cooking spray; place on hot grill rack, cover and cook 8 minutes or until internal temperature reaches 160°, turning once.
Spread 1 side of bread slices with remaining 2 tablespoons butter. Place 4 bread slices, buttered side down, on work surface, top with cheese spread, onion mixture, patties and remaining 4 bread slices, buttered side up.
Place patty melts on hot grill rack; cover and cook 4 minutes or until heated through and grill marks appear, turning once.
Approximate nutritional values per serving (1 patty melt): 761 Calories, 44g Fat, 18g Saturated Fat, 148mg Cholesterol, 1299mg Sodium, 53g Carbohydrates, 2g Fiber, 11g Sugars, 7g Added Sugars, 32g Protein