Preheat oven to 300 degrees.
In a stand mixer, mix butter, brown sugar, vanilla and egg white.
Mix until nice and creamy.
In a medium bowl, combine the rice flour, salt, icing sugar, cornstarch, tapioca starch and xanthan gum.
Make sure it is fully mixed.
Then, add dry ingredients to the creamed mixture, a little at a time, until it looks like a thick whipped cream.
Next, line a cookie sheet with parchment paper.
Using a small ice cream scoop, scoop out dough balls and place on the cookie sheet.
Sprinkle some cookies with Meyer lemon peel.
Mix in a little vanilla powder into some of the dough and bake in the oven.
Sprinkle some cookies with Rose/Vanilla Sugar.
Bake the cookies for 10-12 minutes until lightly golden.
I keep my shortbread in the refrigerator and find that a cold shortbread cookie tastes the best!
The cold really brings out the buttery smooth flavour and tends to taste less dry like most shortbread recipes.