Preheat oven to 400°F (200°C).
Heat a skillet over medium heat and melt the butter. Add the onions and stir gently to coat. Cook for 5-7 minutes, scraping up any fond that forms on the bottom. Set aside.
Spread the pizza crust on a pizza pan. Spread the white garlic Alfredo sauce over the crust.
Sprinkle the mozzarella and feta evenly over the sauce. Top with shredded turkey, cooked onions, and sliced garlic.
Bake for 20 minutes or until the crust is golden and the cheese is melted.
For the cranberry vinaigrette, blend the cranberry sauce, apple cider vinegar, and olive oil until smooth. Season with salt and pepper to taste.
Cut the pizza into wedges and drizzle the cranberry vinaigrette on top. Sprinkle additional feta if desired.