Preheat an oven to 350F. Grease a 9-inch cake pan or springform pan with butter and then add the granulated sugar and turn the springform pan moving the sugar around the pan until it is coated. Dispose of extra granulated sugar. Set aside.
In a medium mixing bowl, combine the gluten-free flour blend, xanthan gum (if using), baking powder, baking soda, salt, ground cinnamon, nutmeg, ginger and cloves. Whisk to combine. Set aside.
In a large mixing bowl, add the apple sauce, sour cream, oil, brown sugar, granulated sugar, egg and vanilla extract. Beat with a mixer until combined.
Gradually add the dry ingredients to the wet ingredients. Mix until no more streaks of flour remain.
Fold in the diced apples.
Pour the batter into the prepared cake pan.
Bake at 350F for 40-45 minutes, until the cake is cooked through and when a toothpick is inserted into the middle it comes out mostly clean with a few moist crumbs.
Remove the cake from the oven and cool in the pan for 20 minutes before inverting onto a cooling rack to finish cooling.