
- Preheat oven to 325 degrees F.
- Coat one 8" x 4" nonstick loaf pan with cooking spray. Set aside.
- Using an electric mixer and a large mixing bowl, cream together the butter and sugar on medium speed until light and fluffy.
- Mix in the eggs on low speed until blended.
- Add the grated lemon peel.
- In a medium bowl, sift together the flours, xanthan gum, baking powder, baking soda, and salt.
- In another medium bowl combine the buttermilk and vanilla.
- On low speed, beat the dry ingredients into the butter mixture, alternating with the buttermilk -- beginning and ending with the dry ingredients.
- Mix just until combined.
- Spoon the batter into the prepared pan and smooth top.
- Bake the cake for about 50 minutes or until top in golden brown and a cake tester inserted into center comes out clean.
- Cool cake in pan for 5 minutes, then remove from pan and cool on rack.