Preheat the oven to 375 degrees Fahrenheit. Grease a 9x13-inch baking dish.
In a large skillet, heat olive oil over medium-high heat. Saute the diced onion and minced garlic until softened.
Add the ground beef to the skillet and cook until evenly browned. Drain any excess fat.
Stir in the crushed tomatoes and Italian seasoning. Reduce heat and simmer for 15 minutes.
In a separate bowl, mix together the ricotta cheese, half of the Parmesan cheese, and a pinch of salt and pepper.
Spread a thin layer of the meat sauce in the bottom of the prepared baking dish.
Layer lasagna noodles over the sauce, followed by a layer of the ricotta mixture, mozzarella cheese, and more meat sauce. Repeat these layers until all ingredients are used, finishing with mozzarella and Parmesan on top.
Cover the baking dish loosely with aluminum foil and bake for 25 minutes.
Remove the foil and bake for an additional 25 minutes, or until the cheese is bubbly and golden brown.
Let the lasagna rest for 15 minutes before slicing. Garnish with fresh parsley and serve.