Preheat the oven to 375 degrees. You will need a 9x13 glass baking dish.
Cook the cilantro lime rice according to package instructions. You could also use cooking bag rice or Minute rice to save time.
Bring water to a boil in a large Dutch oven. Cut the peppers in half and place in boiling water for 3-5 minutes or until they barely begin to soften. Make sure you don't cook them. This process helps them bake completely so they aren't crunchy. Place the peppers in the glass baking dish.
In a small frying pan heat the olive oil and cook onions and garlic until softened and transluscent.
Mix the ground beef, Italian sausage, cooked onions and garlic, salt, pepper, oregano, basil, parsley, dried red pepper flakes, diced tomatoes, and baby spinach in a large bowl.
When rice is cooked let it cool for a few minutes and then add it to the meat mixture.
Fill the pepper halves with the meat mixture. I prefer not to cook my meat mixture ahead of time. It will thoroughly cook as the peppers bake and it gives the peppers more moisture.
Drizzle ketchup over the meat from the bottle.
Bake in 375 degree oven for about 30 minutes or until peppers are tender.
Remove from oven and add grated mozzarella cheese to the top of the peppers.
Place peppers back in the oven for about 5 minutes or until cheese is nice and melted.