Set a pizza stone on the bottom of the oven and preheat the oven to 450°.
In a pan set over medium heat, brown the meat and onions, until cooked through and tender. Drain. Follow the directions on the packet of taco seasoning. Set aside.
In a small bowl, combine the refried beans with the chili powder and cumin and mix until fully incorporated.
Stretch the pizza dough to a 12-inch round and transfer to a cornmeal or flour-dusted cutting board.
Spread the bean mixture on top, leaving a 1/2- inch border. Sprinkle with ¾ of the cheese followed by the taco meat, then remaining cheese.
Slide the pizza onto the preheated stone and bake for 12-15 minutes, until the bottom is crisp and the cheese is bubbling. Top with the lettuce, dollops of sour cream, tomatoes, olives and peppers.
Cut into 8 wedges and serve.
