In a small bowl, whisk together water, tamari or coconut aminos, brown sugar substitute, minced garlic, minced ginger, and toasted sesame oil until well combined. Set aside.

Heat avocado oil in a large skillet over medium-high heat. Add ground beef and white parts of green onions. Cook for 5 to 7 minutes, breaking apart, until browned. Drain excess grease.

Pour the prepared sauce over the browned beef in the skillet. Stir and simmer over medium heat. Sprinkle xanthan gum while whisking until sauce thickens (1 to 2 minutes).

Remove from heat and top with reserved green onion greens and sesame seeds if desired. Serve hot over cauliflower rice or zucchini noodles.