In a small bowl, mix the sugars, apple pie spice, and salt until well combined to create the sugar mixture. Set aside.
In a 9x13 inch baking dish, add 4 tablespoons butter and melt in the microwave or oven. Swirl or use a brush to spread butter up the sides.
Add sourdough dough and spread over the dish.
Sprinkle with about ⅓ cup of the sugar mixture and apples.
Pick up one end of the dough from the short side and bring it to the middle. Repeat on the other end so that they meet in the middle and the apples are covered. Gently press the dough out to evenly cover the baking dish.
Cover with plastic wrap for 1 to 2 hours until slightly puffy, or about doubled in size.
Meanwhile, preheat oven to 425°F.
Melt 2 Tablespoons of butter and sprinkle or brush over the dough. Sprinkle about ⅓ cup sugar mixture over the top.
Coat fingers in melted butter and dimple the dough, pressing all the way to the bottom.
Bake for 20 to 30 minutes, or until the bread is golden brown and the internal temperature reaches 200 to 205°F. Remove from the oven and sprinkle with remaining sugar mixture. Allow to rest for at least 20 minutes before cutting and serving. Serve with ice cream or whipped cream if desired.
Notes
*You can also use your favorite sourdough or a plain focaccia dough recipe. Or prepare a 2 pound sourdough loaf, and allow it to "overproof" overnight on the counter.**If you don't have apple pie spice, make it with 2 teaspoons cinnamon, 1 teaspoon cardamom (optional), and ½ teaspoon nutmeg (optional).
Store at room temperature for 2 days or in the refrigerator for 5 days.
To reheat, microwave for 20 seconds or reheat in the air fryer.