Preheat the oven to 350 F° and prepare a baking sheet with parchment paper.
In small bowl, stir together the flax meal, water and lemon juice. Set aside to gel for five minutes.
Meanwhile, in a bowl of a stand alone mixer, cream together the butter and sugars using a paddle attachment until light and fluffy, about 2-3 minutes. You may need to stop and scrape the sides from time to time. Add in the flax meal mixture and vanilla and combine.
In another bowl, whisk together the flour, baking soda, salt and lemon zest to combine. Slowly add the dry mixture to the bowl of the mixer and combine on a low speed. Once almost combined and a few flour streaks remain remove the paddle and gently fold in the frozen blueberries using a rubber spatula just until combined. Don't over mix or you will have entirely blue cookies.
Use a 1 ½ inch cookie scooper to scoop and drop the cookies onto the baking sheet about 2" apart. Bake the cookies for 11-14 minutes and the edges are golden. Let lemon blueberry cookies cool on the baking tray for 10 minutes before transferring them to a cooling rack to continue cooling.
Stir together the powdered sugar and lemon juice. Add the almond milk 1 tablespoon at a time until you reach a pourable consistency. Drizzle the glaze over the cookies and top with lemon zest if desired. Serve.