Begin by placing the almond flour into a skillet over medium heat on the stovetop. Stir constantly until the almond flour is toasted. Remove from the heat, pour into a bowl, and set aside to cool.
In a medium bowl, whisk together the flour, cinnamon, salt, and lemon zest. Then, set the bowl aside.
In the bowl of a stand mixer (or a large bowl if using a hand mixer), cream together the butter and sugar until light and fluffy (approximately 3 minutes).
Beat in the vanilla and egg yolks on low speed. Stir in the almond flour until just mixed and then add the all-purpose flour until incorporated.
Divide the dough in half, cover in plastic wrap, and refrigerate for 1 hour (or until firm). This allows the dough to relax and the butter to firm up, so the cookies won’t spread when baking.