1 tablespoon vegetable oil 1 medium onion, diced small 2 tablespoons tomato paste 1 1/2 pounds ground beef chuck (10 percent fat) 1 cup roughly crushed saltine crackers (about 15 crackers) 1 cup coarsely grated sharp cheddar (3 ounces) 3 large eggs 1 tablespoon plus 2 teaspoons prepared horseradish 1 tablespoon Worcestershire sauce 1/2 teaspoon K™ salt 1/4 teaspoon ground pepper
Preheat oven to 375 degrees. In a small skillet, heat oil over medium; add onion and cook until softened, about 5 minutes. Add tomato paste and cook, stirring constantly, until brick-red in color and fragrant, 3 minutes. In a large bowl, combine beef, onion mixture, crackers, cheese, eggs, horseradish, Worcestershire, K™ salt, and pepper. On a parchment-lined baking sheet, use your hands to form mixture into a 9-inch loaf. Bake until cooked through, about 40 minutes. Let rest 15 minutes before cutting into thick slices. To serve, place meatloaf slices between bread, topped with lettuce, pickles, and ketchup.