Preheat and Prep: Preheat your oven to 375°F and line one muffin pan with parchment paper liners.
Dry Ingredients: In a large mixing bowl, whisk together the gluten-free flour, baking powder, baking soda, guar gum and salt.
Wet Ingredients: In a stand mixer fitted with a paddle attachment, mix together the eggs, dark brown sugar, maple syrup, yogurt, milk, and vanilla extract until well combined.
Combine Ingredients: Turn the mixer to low speed and gradually add the dry ingredients to the wet mixture, blending until the flour is fully incorporated.
Add Fats: With the mixer on medium-low speed, slowly add the melted butter and oil to the batter. Mix until the butter is fully incorporated, then turn off the mixer.
Mix-Ins: In a small bowl combine the shredded apples (I use my cheese grater to shred the apples), cinnamon and nutmeg until the apples are coated in cinnamon delight! Fold in the 2 cups of apples into the batter until evenly distributed.
Crumble: In another small bowl, whisk together the flour, brown sugar, cinnamon and nutmeg. Cube the butter, then using your fingers or a fork, cut the butter into the flour mixture.
Fill Muffin Tins: Using a scoop or spoon, fill each muffin cups about 3/4 of the way full with the muffin batter. Then sprinkle the brown sugar crumb atop the muffins.
Bake: Place the muffin pan into the preheated oven, and bake for 15 minutes, checking them at the 10-minute mark to avoid overbaking. The tops of the muffins should be slightly brown.
Cool and Enjoy: Once baked, remove the muffin tin from the oven and allow them to cool in the pan for a few minutes before transferring to a wire rack or cooling rack to cool completely. Enjoy your delicious homemade muffins!