On a cutting board, cut the pepper and onion into very thin slices. Add to large skillet with light oil cooking spray.
In a large skillet, over medium heat, saute the peppers and onions for 10-15 minutes on low heat until soft and translucent.
Cook the brown rice according to package directions.
Heat a large skillet over medium heat. Add the cauliflower rice and cook until softened, about 5 minutes.
Warm the shredded beef in the oven, microwave or a skillet.
Add the shredded beef, peppers and onions, and jalapeños to the skillet and cook until heated through, about 3 minutes.
Assemble your taco bowls.
Top with the cauliflower rice, brown rice, shredded beef mixture, sour cream, and cheese. Garnish with avocado and additional jalapeños, if desired.