Heat the olive oil in a large skillet over medium-high heat. Add the diced onion and sauté for 3-4 minutes until softened.

Add the ground beef to the skillet. Cook, breaking it apart with a wooden spoon, until fully browned. Drain any excess grease from the pan.

Stir in the minced garlic, taco seasoning, and water. Simmer for 2-3 minutes until the liquid has mostly evaporated and the beef is well-coated.

Add the cauliflower rice to the skillet with the beef. Stir to combine and cook for 5-6 minutes until the cauliflower is tender but still has a slight bite.

Fold in the rinsed black beans and cook for another 2 minutes until heated through.

Remove from heat and stir in the fresh lime juice and chopped cilantro. Serve in bowls topped with sliced avocado.