Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
In a mixing bowl, whisk together almond flour, Parmesan cheese, garlic powder, onion powder, salt, and black pepper.
In a separate bowl, beat the egg. Dip each cauliflower floret into the egg, allowing the excess to drip off, then coat it in the almond flour mixture. Place the coated florets on the prepared baking sheet.
Bake the cauliflower in the preheated oven for 20-25 minutes, flipping halfway through, until golden brown and crispy.
In a medium saucepan over medium heat, combine apple cider vinegar, soy sauce, sugar-free ketchup, erythritol, ginger, garlic, and sesame oil. Stir well and bring to a simmer.
If you prefer a thicker sauce, sprinkle in the xanthan gum while whisking continuously until the sauce reaches your desired consistency. Remove from heat.
Once the cauliflower is done baking, transfer it to a large mixing bowl. Pour the sweet and sour sauce over the crispy cauliflower and gently toss until all the florets are well coated.
Serve immediately, garnished with sesame seeds or chopped green onions if desired. Enjoy your delicious Keto-Friendly Sweet and Sour Cauliflower!