In a pot over medium heat, add the ground beef, breaking up as it cooks. Cook until meat is starting to turn brown, about ten minutes. Add taco seasoning and stir to combine. Create a hole in the center by pushing the meat to the sides of the pan, add onion and cook for 3 - 4 minutes. Stir to combine the taco meat, and onion. Continue to cook for another 2 -3 minutes, stirring occasionally.
Add cup of rice, and stir to coat rice in taco seasoning, add tomato sauce, and beef broth. Stir, and bring to a simmer. Lower heat, and cook covered for 25 - 30 minutes, until rice has absorbed all the liquid.
While the rice mixture cooks, heat your oven to 350° and bring another large pot of water to a boil.
Once water is boiling, take your peppers and submerge them in the boiling water. This may take two or three rounds depending on the size of your pot. I usually do three at a time. Let peppers sit in boiling water for 1 - 2 minutes, until they are bright green.
Set peppers aside in a 9x13 baking pan. When the rice is finished cooking, add the shredded cheese, reserving 1/2 cup for the top of the peppers. Mix in the cheese until melted and thoroughly combined.
Scoop rice mixture into the peppers, top with remaining cheddar cheese, and cook in oven for 15 minutes. Let cool and either store for lunch or eat them all right away!