In a small saucepan, combine blueberries and 1 tablespoon sugar. Simmer over medium heat for 10-15 minutes until reduced to a thick jam. Let cool completely.

In a medium bowl, whisk together flour, baking powder, and salt.

In a large bowl, cream softened butter, granulated sugar, and brown sugar until light and fluffy (2-3 mins).

Beat in the egg, vanilla extract, and lemon zest.

Mix in the cooled blueberry reduction until the batter is uniformly purple.

Gradually add dry ingredients, mixing until just combined. The dough will be sticky.

Cover and refrigerate dough for at least 2 hours (up to overnight) to firm up.

Preheat oven to 350°F (175°C). Line baking sheets with parchment paper.

Scoop 1.5 tbsp portions of dough, roll into balls, then roll generously in powdered sugar.

Bake for 11-13 minutes until puffed and cracked. Cool on pan for 5 minutes before transferring to wire rack.