Heat the Oil: Pour 1 tablespoon of oil into a large skillet over medium-high heat and let it warm for about 1 minute until shimmering.
Brown the Beef: Add the ground beef to the skillet and cook for 5 to 7 minutes, breaking it apart with a spoon as it browns, until no pink remains and the meat is fully cooked through.
Sauté the Vegetables: Add the diced onion and bell pepper to the beef and cook for 3 to 4 minutes, stirring occasionally, until the vegetables soften.
Add Seasoning and Sauce: Sprinkle the taco seasoning over the beef and vegetables, then pour in the can of diced tomatoes and chilies along with 1/2 cup of water, stirring well to combine all ingredients.
Simmer: Reduce heat to medium and let the mixture simmer for 5 minutes, allowing the flavors to meld and the liquid to reduce slightly.
Cook the Cauliflower Rice (Stovetop): In a separate skillet over medium heat, add the frozen cauliflower rice directly and cook for 6 to 8 minutes, stirring occasionally, until warmed through and any excess moisture has evaporated.
Cook the Cauliflower Rice (Microwave): Alternatively, place the frozen cauliflower rice in a microwave-safe dish, cover loosely, and microwave on high for 4 to 5 minutes, stirring halfway through, until heated through.
Start with the Base: Divide the warm cauliflower rice among serving bowls or plates, creating an even layer on the bottom of each.
Layer the Beef: Spoon the cheesy taco beef mixture over the cauliflower rice, distributing the meat and sauce evenly.
Top with Cheese: Sprinkle the shredded cheddar cheese generously over each bowl, allowing some to melt from the heat of the beef.
Garnish: Add optional toppings like fresh cilantro, green onions, jalapeños, or a dollop of sour cream if desired.