Let's cook.
Preheat your oven to 375 degrees Fahrenheit and grease a shallow baking dish.
Heat a large skillet over medium heat and brown the ground beef with the diced onion until fully cooked through.
Stir the cooked rice, cinnamon, allspice, and half of the tomato sauce into the beef mixture until well combined.
Fold in the toasted pine nuts and remove the skillet from the heat.
Stand the bell peppers upright in the baking dish and divide the beef and rice mixture evenly among them.
Pour the remaining tomato sauce over the tops of the stuffed peppers.
Cover the dish with foil and bake for 35 minutes, then remove the foil and bake for another 10 minutes until the peppers are tender.
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