01 - Set oven temperature to 375°F (190°C) and allow to come to temperature.
02 - Warm olive oil in a large skillet over medium heat. Sauté diced onion for 2–3 minutes until translucent, then add minced garlic and cook for 1 additional minute.
03 - Add ground beef or Italian sausage to the skillet and cook, breaking into crumbles, until browned, about 5 minutes. Drain excess fat if needed.
04 - Incorporate diced tomatoes with juice, chopped spinach, dried basil, dried oregano, crushed red pepper flakes, salt, and black pepper. Stir and cook for 2 minutes.
05 - Stir in low-sodium broth and lasagne noodles. Mix thoroughly, cover, and simmer for 7–8 minutes until the noodles are just al dente. Remove from heat.
06 - Fold in 1/2 cup mozzarella and all ricotta cheese until combined and creamy.
07 - Stuff each prepared bell pepper with the hot lasagne mixture.
08 - Set peppers upright in a 9x13-inch baking dish. Distribute remaining 1/2 cup mozzarella and Parmesan cheese evenly on top.
09 - Pour a splash of water into the baking dish base. Cover tightly with foil and bake for 25 minutes.
10 - Remove foil and continue baking for 10 minutes until peppers are tender and cheese is golden brown and bubbly.
11 - Allow peppers to rest for 5 minutes before serving hot.