Meatloaf with stuffing and Marmalade Glaze

recipe resource here 

1 1/2 pounds ground beef (preferably chuck)
2 cups cooked stuffing, roughly chopped
1 large egg, beaten
kosher salt and black pepper
1/4 cup orange marmalade
1/4 cup whole-grain mustard
10 ounces baby arugula (about 6 cups)
2 tablespoons extra-virgin olive oil
2 tablespoons balsamic vinegar

Heat oven to 400° F. In a large bowl, combine the beef, stuffing, egg, 3/4 teaspoon salt, and 1/2 teaspoon pepper. Transfer the mixture to a rimmed baking sheet and form it into a 9-inch loaf (about 2 1/2 inches thick). Bake for 30 minutes. In a small bowl, combine the marmalade and mustard. Spread on the meat loaf and continue to bake until cooked through, 15 to 20 minutes. Let rest for 10 minutes before slicing. Divide the arugula among plates. Drizzle with the oil and vinegar. Serve with the meat loaf.