Preheat oven to 325° F. Prepare a 10 inch bundt pan by generously coating with cooking spray. Set aside.
In a medium bowl, sift gluten free flour, guar or xanthan gum (omit if already in your flour blend), cinnamon, nutmeg, salt and baking soda. Set aside.
In a large mixing bowl, combine oil and sugar. Add eggs and vanilla extract and stir until combined. Combine in sour cream until most clumps are gone. Gently stir in apples.
Pour flour mixture into apple mixture and combine until all flour is mixed in. Your batter should be slightly thick, but runny enough to pour into pan.
Pour batter into prepared bundt pan and gently shake the pan to distribute the batter evenly.
Bake for 60-65 minutes. The cake will be slightly risen above the pan with a dark golden color and an inserted toothpick will come out clean. Remove from oven and allow to cool for 20-30 minutes before removing from pan.
When ready to remove from pan, gently slide a knife around all edges of the cake, both on the inside ring and on the outer edges. Using a cooling rack or platter, flip the cake out (I like to turn the rack upside down on top of the bundt pan, and then flip it over so the cake falls out). Allow cake to cool completely before frosting so the frosting doesn't run off cake.