In a large bowl, add the dry ingredients and whisk to blend.
In a smaller bowl, add the wet ingredients and mix well. Add the apple slices.
Pour the wet ingredients into the dry ingredients and mix. (See Notes below)
Place liners into the muffin tin and fill each cup about ¾ full of muffin batter.
Bake for 25 minutes until done. Check at the 20 minute mark by inserting a toothpick into the top of a muffin. If the toothpick comes out clean, the muffins are ready.
Remove from the oven and cool on a cooling rack.
I have tested this recipe with King Arthur Measure for Measure GF, Bob's Red Mill 1 to 1 GF blend, and Authentic Foods Multi Blend in this recipe. That doesn't mean others will not work, I just have not tested other flours.
If your gluten free flour blend doesn’t contain Xanthan Gum or Guar Gum, please add 1 teaspoon.
To test for doneness, insert a toothpick into the center of a muffin. If the toothpick comes out clean, it is done baking. If you see batter or crumbs, the muffins need to bake longer.
The secret to light and fluffy muffins is to just barely mix the batter. If you overmix the batter, your muffins will be denser.
If you want your muffins to have a domed style top, bake at 425º F for the first 5 minutes then reduce the temperature to 350º.
These muffins will keep up to 4 days in an air-tight container, or up to 4 months in the freezer.