Cook the Beef: In a skillet over medium heat, add the diced onion and garlic, and sauté until softened. Add the ground beef and cook until browned. Stir in the taco seasoning and diced tomatoes, and let simmer for 5 minutes.
Prepare the Cauliflower Rice: In another pan, heat olive oil over medium heat. Add the grated cauliflower and sauté for 5-7 minutes until tender. Season with salt and pepper to taste.
Assemble the Bowls: Start with a base of cauliflower rice in each bowl. Top with the seasoned beef mixture, then add shredded lettuce, cheese, sour cream, and any additional toppings you prefer.
Garnish and Serve: Finish with a sprinkle of sliced jalapeños and chopped cilantro. Serve with lime wedges on the side for an extra burst of flavor.