In the stand mixer bowl, beat butter until light and fluffy, about 30 seconds.
Add in sugar, brown sugar, maple syrup, baking soda, cream of tartar, and salt. Beat until well combined.
Add in the egg and the egg yolk. Beat until combined.
Add in the vanilla extract. Beat until well combined.
Add in the flour, about 1/2 cup at a time. Scrape the sides and mix again until everything is combined.
Chill dough for 30 minutes to 1 hour.
Preheat the oven to 325 degrees Fahrenheit. Line baking sheet with parchment paper.
Roll dough into about 1” balls, and roll in cinnamon sugar.
Place dough on the baking sheets, making sure they are spaced out evenly, about 2-3” apart (these cookies expand).
Bake for about 12-14 minutes, or until the edges are slightly brown. Allow cookies to cool a few minutes before removing them from the tray and cool completely on wire rack.
Maple Glaze
Over low heat, melt butter, maple syrup and vanilla extract together. Once everything is melted, remove from the heat.
Sift in powdered sugar and whisk until fully combined. Allow the icing to cool about 8-10 minutes, which allows the glaze to thicken.
Once the glaze has thickened, give it a quick stir then drizzle it over the cookies with a spoon. If the glaze hardened, heat up in low heat for a few seconds.