Brown the ground beef in a large sauce pan over medium heat, breaking the beef into small pieces as it browns. Season the beef with the salt, ground black pepper, dried oregano, and red pepper flakes.
When the beef is cooked through add the diced onions and pepperoni and cook over medium-low heat for 3 to 5 minutes, until the onions are cooked through (translucent).
Pre-heat the oven to Hi-Broil.
Add the pizza sauce and simmer for another 5 to 10 minutes.
While the Sloppy Giuseppe simmers, spread garlic butter over the top and bottom buns. Place the buns on an aluminum foil lined baking pan and toast the buns on the top rack in the oven on hi-broil for 1 to 2 minutes. Ensure that you keep an eye on the buns so they do not burn. It may take more than one iteration to toast all of the buns.
Then add 1/2 off the mozzarella to the Sloppy Giuseppe and melt to thicken.
Place 1/4 Cup or as much of the Sloppy Giuseppe on the bun that you would like. Top with a sprinkle of mozzarella and enjoy.
Sauté the onions, crushed red pepper, and minced garlic in a pan with olive oil over medium heat until the onions are translucent, about 3 to 5 minutes. Season with salt and pepper. Set the mixture aside in a small bowl to cool.
Preheat your oven to 350 degrees F.
Once the onion mixture has cooled to the touch, place the onion mixture and the remaining meatloaf ingredients except for the mozzarella cheese in a large bowl.
With your hands, mix thoroughly to combine but be careful not to over mix.
Form the meatloaf mixture into a football shape by hand on a baking pan lined with aluminum foil. You can also cook it in a meatloaf pan if you desire.
Remove the meatloaf and let rest for 5 minutes. Set your oven to broil.
Slice the meatloaf and place on a baking pan lined with aluminum foil. Top with a large spoonful of marinara sauce and a handful of mozzarella.
Broil on the top rack until the cheese is melted while being careful not to burn the cheese.
Top with fresh herbs, grated parmesan, and serve on top of your favorite pasta, by itself, between some slices of toasted garlic bread, whatever you crave!