1. Brown the Ground Meat: In a large skillet, cook the ground beef and chopped onion over medium heat. Break up the meat with a spoon as it cooks. Continue until the beef is fully browned and the onion is softened, about 5-7 minutes. Drain any excess grease from the skillet.

2. Season the Mixture: Stir in the tomato sauce, diced tomatoes (with their liquid), Italian seasoning, and garlic powder into the skillet with the browned meat. Mix everything well to combine.

3. Simmer the Sauce: Bring the mixture to a gentle simmer, then reduce the heat to low. Let it cook for about 5-7 minutes, allowing the flavors to meld and the sauce to thicken slightly. Season with salt and black pepper to your taste.

4. Prepare the Crescent Rolls: While the sauce simmers, unroll the crescent roll dough onto a baking sheet. If using perforated dough, press the seams together to form a single sheet. If using seamless dough, simply unroll it.

5. Assemble the Dish: Spoon the meat sauce evenly over the crescent roll dough, leaving a small border around the edges. Sprinkle the shredded mozzarella cheese over the meat sauce.

6. Bake to Golden Perfection: Carefully roll up the crescent dough from one long side to the other, creating a log. Pinch the ends to seal. Bake in a preheated oven at 375 F (190 C) for 15-20 minutes, or until the crescent roll is golden brown and the cheese is bubbly.

7. Rest and Serve: Remove from the oven and let it rest for 5 minutes before slicing into individual portions. This helps the filling set and makes for cleaner slices.