In a large bowl, whisk together the gluten free flour, instant yeast, sugar, salt, and xanthan gum. Add the warm water, olive oil, and apple cider vinegar and stir until a soft dough forms. Cover the bowl with a damp towel and let it rest in a warm spot for 30 minutes.
While the dough rises, stir together the mayonnaise, ketchup, yellow mustard, pickle relish, garlic powder, and smoked paprika in a small bowl until smooth. Set the burger sauce aside in the fridge.
Season the ground beef with salt, pepper, and onion powder. Heat a large skillet over high heat and add the beef, pressing it flat with a spatula to get a good sear. Cook for 4 to 5 minutes, breaking it into crumbles as it browns.
Drain any excess grease and set the cooked beef aside.
Preheat your oven to 450 F. Line a large baking sheet with parchment paper and lightly oil it. Transfer the dough onto the prepared sheet and press it out into a 14-inch round or rectangle using oiled hands, pushing the edges up slightly to create a rim.
Par-bake the crust for 8 minutes until it is just set and starting to turn lightly golden on the edges. Remove it from the oven.
Spread a thin layer of the burger sauce over the par-baked crust, then scatter the shredded mozzarella evenly over the top. Distribute the cooked ground beef across the pizza and lay the American cheese slices over the beef.
Return the pizza to the oven and bake for 10 to 12 minutes until the cheese is melted and bubbly and the crust is golden and crisp on the bottom.
Remove the pizza from the oven and immediately top it with the diced onion, pickle slices, and shredded lettuce. Drizzle extra burger sauce over the top and sprinkle with sesame seeds. Slice and serve right away.