MAKE-AHEAD PIZZA BURGERS

Steps:

• Preheat oven to 350 degrees F (175 degrees C).
• Place onion and celery into a pot and cover with water; bring to a boil. Simmer until tender, about 3 minutes. Drain.
• Heat a large skillet over medium-high heat; cook and stir beef until it is crumbly, evenly browned, and no longer pink, about 5 minutes. Drain and discard any excess grease. Stir in onion mixture, ketchup, tomato soup, 1/2 can tomato paste, garlic salt, salt, and pepper; set aside to cool.
• Mix remaining 1 1/2 cans tomato paste, oregano, and sugar in a small bowl. Season with salt and pepper.
• Butter each English muffin half, then spread with tomato paste mixture. Divide ground beef mixture over each muffin half and top with strips of American cheese. Place open-faced sandwiches on large baking sheets.
• Bake in the preheated oven until cheese melts, about 15 minutes.