Heat a large skillet over medium-high heat and add the ground beef, breaking it apart with a spoon as it cooks until it's no longer pink and has developed some browning, about 5-7 minutes. Drain off excess fat by tilting the pan and using a spoon to push the meat to the side, letting the grease pool before carefully pouring it out. This step removes unwanted fat while keeping the flavorful browned bits that will anchor the dish. Add the onion powder and garlic powder directly to the hot meat and stir constantly for about 30 seconds to toast the spices and release their aromatics—I find this quick toasting step makes a huge difference in the final flavor depth compared to adding them raw.

Add the cream of mushroom soup directly to the browned beef and stir well to combine, breaking up any clumps. Pour in the diced tomatoes with their juice and the uncooked rice, stirring everything together until the rice is evenly distributed and coated with the soup and tomato mixture. The soup and tomatoes will create the liquid needed to cook the rice. Taste the mixture and season with salt and pepper to your preference—I season at this stage rather than waiting until the end because it gives the rice time to absorb the flavors as it cooks.

Transfer the mixture from the skillet to a 9x13 inch baking dish or similar-sized casserole dish, spreading it into an even layer. Cover the dish tightly with foil or a lid and place it in a 350°F oven (or leave it on the stovetop over medium-low heat, covered with a lid, if preferred). Simmer for 15 minutes until the rice has absorbed most of the liquid and is tender. The covered, gentle cooking ensures the rice cooks evenly and the flavors meld together without the mixture drying out.

Remove the casserole from the oven and carefully take off the foil or lid (watch out for steam). Sprinkle the mozzarella cheese evenly over the top of the casserole in an even layer. Set your oven to broil on high and place the casserole on the middle rack, watching it carefully for 2-3 minutes until the cheese is melted and lightly golden—don't walk away, as broilers heat quickly and the cheese can go from perfect to burnt in seconds. The high, direct heat of the broiler melts the cheese beautifully while slightly crisping the edges.