• Break the 16 ounces of lasagna noodles into roughly 2-inch pieces. Cook them according to the package directions until al dente, then drain and set aside.
• Meanwhile, heat the oven to 350°F and coat a 12×17-inch sheet pan with nonstick cooking spray.
• Place the spinach in a medium skillet and sauté over medium heat. After about 2 to 3 minutes, it will wilt and reduce in volume. Remove from heat.
• In a medium mixing bowl, combine the ricotta cheese with the cooked spinach. Season with salt and pepper as desired, then set aside.
• Warm the olive oil in a large skillet over medium-high heat. Add the ground beef and onion, cooking until beef is fully browned. Stir in the garlic. Cook for another minute. Drain any excess fat, then add the marinara sauce. Season the sauce with Italian seasoning, along with salt and pepper, to taste.
• Add the cooked noodles to the meat sauce and gently mix until evenly coated.

To Assemble

• Transfer the meat and noodle mixture to the prepared sheet pan and spread it into an even layer.
• Spoon dollops of the ricotta mixture evenly over the top.
• Finish by sprinkling the mozzarella and the Parmesan cheeses evenly over the top.
• Bake uncovered for 25 to 30 minutes, or until the cheese is melted, bubbly, and lightly browned.
• Let the lasagna rest for a few minutes before serving. Enjoy!