Preheat and Prep: Preheat your oven to 425°F (220°C) and line two muffin pans with parchment paper liners.
Dry Ingredients: In a medium 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 to the batter. Mix until the butter is fully incorporated, then turn off the mixer.
Mix-Ins: Fold in 2 1/2 cups of your favorite mix-ins such as berries, mini chocolate chips, or nuts. Alternatively, divide the batter into two bowls and add different mix-ins to each for variety.
Fill Muffin Tins: Using a scoop or spoon, fill each muffin cups about 3/4 of the way full with batter.
Bake: Place the muffin pan or pans in the oven and bake at 425°F (220°C) for 5 minutes. Without opening the oven, reduce the temperature to 350°F (175°C) and bake for an additional 15 minutes, checking them at the 10-minute mark to avoid overbaking.
Cool and Enjoy: Once baked, remove the muffins 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!