Preheat your oven to 375°F (190°C).
Slice the bell peppers in half lengthwise and remove the seeds and membranes.
In a large skillet over medium heat, add the olive oil and sauté the finely diced yellow onion and minced garlic until translucent.
Add the ground beef to the skillet, breaking it up with a spatula, and cook until fully browned.
Stir in the cooked brown rice, tomato puree, sea salt, black pepper, dried oregano, and smoked paprika until the mixture is well combined and fragrant.
Arrange the pepper halves in a baking dish and fill each cavity generously with the beef and rice mixture.
Pour 1/4 cup of water into the bottom of the dish, cover tightly with foil, and bake for 30 minutes.
Remove the foil and bake for an additional 5-10 minutes until the peppers are tender and the tops are slightly golden.