Make the Cookies
Wash and dry all 3 lemons. Take a zester and zest all 3 lemons. Put the zest in a little bowl and cover with plastic wrap so it doesn't get crunchy. Set aside.

Take one lemon, cut it in half and juice it. Make sure to remove any seeds if they get in the juice. Set aside.
There should be about 2 tablespoons of juice. If there isn't enough, juice another lemon.

Measure out ½ cup frozen raspberries. Rough chop the raspberries into small pieces. Be careful not to over chop; you don't want a puddle of raspberry pulp.
Place the chopped raspberries into a freezer safe bowl and pop back into the freezer until you're ready to add them into the dough

In a large bowl, whisk together the gluten free flour, baking powder and salt. Set aside.
In a small bowl, using a spoon, mix together the 2 heaping tablespoons of cornstarch with 3 tablespoons of water until thin and watery. It will be thick and tacky at first.

In a large bowl of an electric mixer fitted with the paddle attachment, beat the butter or vegan baking stick and 1 ¼ cups of the sugar until it is soft and creamy. About 2-3 minutes.
Slowly beat the cornstarch water mixture, milk, 1 tablespoon of lemon zest and the 2 tablespoons of lemon juice into the creamed butter and sugar. It will look pale yellow and chunky.

Slowly beat in the gluten free flour mixture a little at a time until just combined

Gently using a spatula, fold in the frozen chopped raspberries. The dough will become a lovely marbled pink color.

Keep the dough in the bowl, cover the top with plastic wrap and freeze for at least 1 hour. You must not skip this step or the cookies will spread everywhere and it must be frozen, not in the fridge.

After 1 hour, preheat the oven to 325 degrees Fahrenheit. Line a baking sheet with parchment paper. Set aside.

Take the dough out of the fridge. Using an ice cream scoop, or a large cookie scoop, scoop the dough out. You should have 11 scoops

In a small bowl, whisk together the remaining 3 tablespoons of granulated sugar and the remaining 1 teaspoon of lemon zest. Mix until completely combined.

Roll each dough ball in the lemon sugar mixture to coat completely.

Place dough balls about 3-4 inches apart on the parchment lined baking sheet. Bake the cookies at 325 degrees Fahrenheit for 15-16 minutes.

Store extra dough balls in the freezer while the rest are baking if they don't all fit. I only bake 6 at a time.

Immediately reshape the cookies when they come out of the oven. Use a spatula to push them into a circle.
Let them cool on the baking sheet for 5 min before transferring to a cooling rack. If you don't do this, the cookies will break apart into a giant mess.
If adding the glaze, let the cookies cool completely before adding it, otherwise the glaze will turn into a liquid mess.

Make the Glaze (If Desired)
In a small bowl, whisk together the 1 cup of confectioners' sugar, 1 or 2 raspberries and the 1 tablespoon plus 1 teaspoon water until combined and smooth.
Drizzle the raspberry glaze on top of the cool cookies. If you drizzle it on warm cookies, the glaze with melt. Let the glaze harden. Sprinkle with more lemon zest if desired.

Notes
For smaller cookies: Use a small cookie scoop and bake at same temperature for 13-14 min. Make sure to keep dough in the fridge in-between baking the batches.