Heat a large cast iron skillet over medium.
When pan is hot, add beef. Break up with spatula and cook until browned, stirring occasionally (about 10 minutes).
While beef is cooking, combine taco seasoning ingredients in a small bowl. Whisk and set aside.
If you're using cauliflower rice, begin to cook that now. When beef is cooked, add 1 cup water to hot pan and stir to lift any stuck browned meats. Add the tomatoes, taco seasoning and arrowroot powder to the pan and mix to thoroughly combine.
Reduce heat and allow to cook down for 10 minutes.
While beef is cooking (and cauliflower rice is doing it's thing!), prep the peppers. Slice bell peppers in half, lengthwise. Remove and discard seeds. Set pepper shells on rimmed baking sheet.
Turn oven to Broil.
Spoon cauliflower rice into taco shells and top with beef. Divide evenly among the peppers. Sprinkle each pepper taco with cheese if using.
Place sheetpan in oven and broil tacos for 3-5 minutes until cheese is bubbling and peppers start to char.
Garnish with cilantro and serve!