Sauté the Vegetables: Heat olive oil in a large skillet over medium heat. Add the cauliflower rice, sliced onions, and bell peppers, stirring occasionally. Cook for about 5–7 minutes until the onions are softened and slightly caramelized. Remove from the skillet and set aside.
Cook the Beef: In the same skillet, sauté the minced garlic until fragrant. Add the beef, season with salt and pepper, and cook until browned, breaking it apart as it cooks. Once done, drain any excess fat.
Combine Ingredients: Return the cooked vegetables to the skillet with the beef. Stir in the Dijon mustard and coconut aminos, ensuring everything is evenly coated. Let it cook for another 2–3 minutes until heated through and well combined.
Melt the Cheese: Arrange the provolone cheese slices on top of the mixture. Cover the skillet and let the cheese melt for about 1–2 minutes, or place under a broiler for a golden, bubbly finish.
Serve and Enjoy: Remove from heat, let it cool slightly, and serve warm. Enjoy your delicious and hearty keto cheesesteak skillet!