Rinse and break the cauliflower head into small florets and roughly chop in a food processor.
In a large skillet, sauté minced onion in 2 tablespoons of olive oil, until softened.
Add ground beef to the skillet and season with salt and pepper. Cook over medium high heat until beef has started to brown and rendered most of its water. Remove from the skillet and set aside.
In the same skillet, add the remaining tablespoon olive oil and sauté cauliflower rice for about 2 minutes. Stir in onion powder, garlic powder, paprika, chili, and cumin. Mix well and continue to cook for a couple of minutes; then add diced tomatoes and broth. Bring to a simmer, and allow the juices to reduce a little. Adjust seasoning if necessary.
Add beef and onion back to the skillet and give a quick stir (you can also keep beef on top of cauliflower for serving if you like). Sprinkle with shredded cheese, cover the skillet and let set for 2-3 minutes off heat to melt cheese.
Garnish with fresh tomatoes, red onion, avocado, Jalapeno, bell pepper, cilantro, and lemon slices.