Zest and juice 1 lemon. Reserve the juice for the cookie dough. In a bowl, add the blueberries, maple syrup, and the zest of 1 lemon and stir around. Let it sit for 1 to 2 hours. Stir it around once in a while to keep the berries rotated. If you use more maple syrup, the blueberries will hold too much liquid and make your cookies too wet and soft.
Preheat your oven to 350° and line 2 cookie pans with parchment paper and set aside. Weigh or measure flour, baking powder, and salt and run a whisk through it to blend and set the bowl aside.
Cream the sugar and butter until light and fluffy using a hand-held or stand mixer. Next, add the vanilla extract, lemon juice, maple syrup, egg, and mix until all are incorporated. Next, you want to slowly add the flour mixture to the wet cookie dough in the mixer bowl. Don't overmix; a minute is good. Next, you want to take the bowl off the stand and, using a one-piece spatula, fold in any flour that the mixer missed.
Now add the whole bowl of infused blueberries and gently fold them into the cookie dough. Try not to break the blueberries but get them as evenly distributed throughout the cookie dough as possible. Refrigerate for 15 to 20 minutes.
I use a medium cookie scooper to add 12 scoops to a cookie sheet pan. Bake at 350° for 13 to 15 minutes until they are just a little brown around the bottom edges. After pulling the cookies out of the oven, let them sit on the cookie pan for at least 3 minutes. They will be soft, so they need a little time to firm up. Then move them to a cooling rack. I left them cool for about an hour on the rack.