Preheat your oven to 375°F (190°C).

In a large mixing bowl, combine the ground beef, breadcrumbs, eggs, garlic powder, onion powder, Italian seasoning, salt, and pepper. Mix until just combined.

In a separate bowl, combine the mozzarella cheese, Parmesan cheese, and spinach (if using) until well blended.

Flatten the meat mixture into a rectangle about 1-inch thick, spread the cheese filling evenly on top, and roll tightly to seal.

Place the meatloaf seam-side down in a baking dish and bake for 45-50 minutes, until the internal temperature reaches 160°F (71°C).

In the last 10 minutes of baking, spread marinara sauce on top and return to the oven.

Once baked, let it rest for 10 minutes before slicing and serving with extra marinara sauce.