Preheat the oven to 375 degrees. In a large bowl, combine the ground beef, sun-dried tomatoes, half the mozzarella, breadcrumbs, egg, Italian seasoning, onion, garlic, salt, and pepper. Mix until evenly blended.
Shape the mixture into a loaf and place it in a baking dish. Bake for 45 minutes.
Remove the meatloaf from the oven and sprinkle the remaining mozzarella over the top. Return it to the oven for 10 more minutes until the cheese melts.
While the meatloaf finishes baking, bring the chicken broth to a boil in a medium saucepan. Slowly whisk in the cornmeal. Reduce the heat and cook, stirring often, for 15 minutes until thick and creamy.
Stir the butter and Parmesan into the polenta. Season with salt and pepper. Slice the meatloaf and serve the portions over the polenta.