Preheat oven to 325 F. Grease an 8×8 glass pan with canola oil.

In a large mixing bowl, add your dry ingredients (allergen-free flour, powdered sugar, chopped rosemary, lemon zest, and salt) and combine thoroughly with a whisk.

Add canola oil to the dry ingredients and mix just until the dough comes completely together.

Pour dough into greased pan and flatten to uniformity across the entirety of the pan. Using a fork, poke holes across the whole the top of the shortbread (this keeps it from puffing oddly).

Bake at 325 for 40-45 minutes, until the edges that can be seen through the side of the pan just start to turn golden-brown.

While the shortbread is baking, add 100 grams of powdered sugar and zest of the remaining ½ of a lemon to a small mixing bowl, and combine with a whisk or spoon. Then, slowly start adding the freshly squeezed lemon juice to the bowl, stirring constantly. Add just enough juice to get to desired texture (mine ended up being most of the ½ of the lemon).

Once the edges of the cookies are starting to brown, remove the pan from the oven and let the shortbread cool in the pan for 20 minutes.

Once the shortbread has cooled, use a bench scraper or sharp knife to cut the shortbread into desired shapes, and remove the shortbread from the pan onto a serving plate.

Drizzle the icing onto the shortbread cookies, as much as desired.