Melt the butter and olive oil over medium high heat in a large, oven safe skillet (I use my 14-inch cast iron skillet. A dutch oven would work too). Add the onion and cook over medium high heat for 5 minutes until lightly golden and fragrant.
Add the garlic, cook for a minute, and then add the beef, Italian seasoning, coconut aminos, sea salt, cumin, and smoked paprika. Stir everything together, and cook until the beef is browned and cooked through.
Add the spinach and bell peppers, and stir to combine. Then add the rice, marinara, and water and stir until everything is combined well. Bring the skillet to a boil, and then reduce to a simmer with a lid on the pan until the rice is cooked through, about 20 minutes.
Once the rice is cooked through, turn the heat off and give the skillet stuffed peppers a stir, tasting for salt to your taste.
Turn the broiler on in your oven to “HI.” Top your skillet stuffed peppers with shredded cheese and place the skillet under the broiler for 2-5 minutes until the cheese is melted and golden to your liking. Every oven broiler runs differently, so check the cheese around 2-3 minutes in case yours runs hot. Mine takes about 5 minutes.