Step 1: Prepare the Meat Sauce

1. Heat a large skillet over medium heat. Add the Italian sausage, diced onion, and bell pepper, and cook until the meat is browned.
2. Stir in the minced garlic, cooking for another 30 seconds.
3. Add the marinara sauce, diced tomatoes, Italian seasoning, salt, and black pepper. Simmer for 10 minutes, then remove from heat.

Step 2: Create the Creamy Cheese Layer

1. In a mixing bowl, combine cream cheese, ricotta cheese, sour cream, egg, and Parmesan cheese.
2. Whisk until smooth and well combined.

Step 3: Assemble the Lasagna

1. Preheat your oven to 375°F (190°C).
2. Spread a thin layer of meat sauce on the bottom of a 9×13-inch baking dish.
3. Add a layer of cooked lasagna noodles.
4. Spread half of the creamy cheese mixture over the noodles.
5. Add another layer of meat sauce and sprinkle with mozzarella cheese.
6. Repeat the layers until all ingredients are used, finishing with a layer of meat sauce and mozzarella cheese.
7. Sprinkle with Parmesan cheese on top.

Step 4: Bake to Perfection

1. Cover with foil and bake for 30 minutes.
2. Remove the foil and bake for another 10 minutes until golden and bubbly.
3. Let the lasagna rest for 10 minutes before slicing.