In the bowl of a stand mixer, cream light brown sugar and softened butter for about 3 minutes until fully creamed. Scrape sides of bowl as needed.
Mix in egg yolk, lemon juice, half of the lemon zest, and half of the lavender.
In a separate bowl, whisk together gluten-free flour, baking soda, and salt.
Slowly add dry ingredients to the wet ingredients in the stand mixer and combine. Once combined, mix the dough for an additional 2-3 minutes for the best results.
While the dough is mixing, prepare the lemon lavender sugar. In a small bowl, stir together white granulated sugar and the remaining lemon zest and lavender. Set aside.
Chill dough in the refrigerator for 3 hours.
Preheat oven to 350°. Prepare baking sheets with parchment paper or silicone baking mats.
Shape dough into 1-inch balls, about the size of a walnut in its shell. I use a #70 small cookie scoop. Roll in the reserved lemon lavender sugar to coat.
Place on prepared baking sheets and bake in the preheated oven for 9-10 minutes. Let rest on baking sheet for 2-3 minutes before transferring to cooling racks.