raditionally, shortbread is not gluten-free as it is made with regular all-purpose wheat flour, which contains gluten. However, this recipe is made gluten-free using Bob’s Red Mill 1-to-1 Gluten-Free Baking Flour, which is a combination of white rice flour, brown rice flour, potato starch, sorghum flour, tapioca flour, and xanthan gum. Using a gluten-free flour blend makes this shortbread suitable for those with celiac disease or gluten sensitivity.