01 -
Preheat the oven to 425°F (220°C) with rack in middle position. In a medium bowl, using your hands, mash the beef with 1 teaspoon salt and the baking soda. Let sit for 20 minutes while continuing with preparation.
02 -
Line a 9x13-inch baking dish with aluminum foil for easy clean-up if desired. Arrange pepper halves cut side up in the baking dish. Drizzle with 1 tablespoon oil and sprinkle with remaining ¼ teaspoon salt.
03 -
Roast peppers for about 20 minutes, until slightly browned and tender-crisp. Some liquid may accumulate in the bottom of the peppers.
04 -
Meanwhile, heat remaining 2 tablespoons oil over medium heat in a large nonstick skillet. Add onion and cook, stirring frequently, until soft and translucent, 3 to 4 minutes. Add garlic and cook 1 minute more, being careful not to brown it.
05 -
Add the ground beef mixture, chili powder, cumin, and oregano to the skillet and increase heat to medium-high. Cook, breaking the meat apart with a wooden spoon, until browned and almost cooked through, 4 to 5 minutes.
06 -
Add tomato sauce and bring to a boil. Reduce heat to medium-low and cook uncovered until meat is fully cooked, 2 to 3 minutes. Stir in the cooked rice and ¾ cup of the cheese until melted. Remove from heat.
07 -
Remove peppers from oven and spoon the meat filling evenly into each pepper half. Sprinkle with remaining ¾ cup cheese. Return to oven and roast for 10 to 15 minutes, until filling is hot and cheese is melted and bubbling.