In a large skillet pan over medium high heat and brown the ground beef until almost cooked through.
Add the onion, and continue to cook until thebeef is browned.
Add the taco seasoning and mix well.
Add the tomatoes and riced broccoli/cauliflower mixture, and stir to combine.
Add the chicken broth, and mix well.
Reduce the heat to medium low, and cook until the broccoli/cauliflower rice begins to soften. (about 3 minutes)
Sprinkle the cheese over the skillet, and cover.
Let cook until the cheese is melted, approximately 3 or 4 minutes.
Remove from heat, and top with avocado, sour cream, and green onions.