If you're using pre-made meatballs, you can skip this step. If you're making your own, follow your favorite meatball recipe and shape the mixture into meatballs. You can make them as small or as large as you prefer.

Heat a large skillet over medium-high heat and add a drizzle of olive oil. Once hot, add the meatballs and sear them on all sides until they are browned and cooked through. Remove them from the skillet and set them aside.

In the same skillet, add a bit more olive oil if needed. Add the diced onion, minced garlic, and sliced bell peppers. Sauté them until they are softened and the onion becomes translucent, which should take about 5-7 minutes.

Pour in the can of diced tomatoes, including the liquid. Stir to combine with the sautéed vegetables. Season the mixture with salt and pepper to taste. You can also add a pinch of Italian seasoning or dried basil for extra flavor.

Place the seared meatballs back into the skillet with the tomato and vegetable mixture. Nestle them into the sauce.

Reduce the heat to low, cover the skillet, and let the meatballs simmer in the sauce for about 15-20 minutes, or until they are heated through and the flavors meld together. Sprinkle the shredded mozzarella cheese evenly over the meatballs and sauce. Cover the skillet again and let it cook for an additional 5-7 minutes, or until the cheese is melted and bubbly.

If desired, garnish the skillet with fresh basil leaves just before serving. Serve the Italian meatball skillet hot, either on its own or with pasta, rice, or crusty bread to soak up the delicious sauce.