Heat a large cast iron skillet over medium high heat. When hot, add ground beef. Cook, stirring frequently, until all the pink disappears. Drain if necessary.
Add taco seasoning mix and cornstarch to the skillet. Omit corn starch if using store bought, prepackaged taco seasoning. Stir until meat is well coated with seasoning.
Add water and stir. Lower heat to medium and simmer, stirring occasionally, for 20 minutes or until most of the liquid has evaporated. Remove from heat and set aside.
Cut sweet bell peppers in half lengthwise. Remove seeds and membranes.
Line a baking sheet with parchment papers. Arrange peppers, cut side up, on the baking sheet.
Divide the meat filling among the peppers.
Sprinkle shredded cheddar cheese over the meat filling.
Bake in a 350 degree oven for 15 minutes or until the cheese has melted and the filling is heated through.
Remove from oven and top with favorite taco toppings.