Preheat your oven to 400°F.
In a food processor, blend the cauliflower florets until rice-like in texture. Transfer the cauliflower rice to a microwave-safe bowl, cover, and microwave on high for about 5 minutes until softened.
Let the cauliflower cool slightly, then place it in a clean towel and squeeze out as much moisture as possible.
Combine the drained cauliflower, egg, mozzarella cheese, garlic powder, onion powder, salt, and pepper in a bowl. Mix until a cohesive dough forms.
Press the mixture evenly onto a lightly greased baking sheet to form a thin crust. Bake in the preheated oven for 20 minutes or until the edges begin to turn golden.
While the crust bakes, warm the pulled chicken (if not already prepared) and mix with 1 tbsp of BBQ sauce (reserve the other tbsp for drizzling).
Remove the baked crust from the oven, spread the BBQ sauce evenly over the base, then layer the pulled chicken on top. Scatter the sliced red onion over the chicken.
Return the pizza to the oven and bake for another 8-10 minutes until the toppings are heated through and the cheese (if any additional is used) is bubbly.
Remove from the oven, slice, and serve immediately.