Add a tablespoon of olive oil to saute pan. Cook the onion on low heat for about 20-25 minutes. Adjust the heat up a touch and add the diced sausage link and cook for another 5-7 minutes.
Preheat oven to 425 degrees and place pizza stone in the oven to preheat. Stack two tortillas on top of each other and place on top of the pizza stone. Cook two minutes on each side. Spread the BBQ sauce on top of the tortillas. Add a layer of white cheddar cheese. Add 1/2 the cooked onions and sausage. Add a layer of mozzarella cheese and bake on the pizza stone for 8 minutes in the 425 degree preheated oven.
This recipe makes two small pizzas so adjust if necessary.
You can use whatever cheese pleases your palate but this is a great combination.