Start by gathering all ingredients, ensuring the butter and egg are at room temperature for optimal mixing. Measure out your sourdough starter, lemon juice, and zest.

Preheat your oven to 375°F (190°C) and line a baking sheet with parchment paper.

In a mixing bowl, combine the softened butter with cane and brown sugars. Beat until light and fluffy.

Mix in the room-temperature egg, lemon extract, lemon juice, and sourdough starter until well blended.

Sift together the flour, baking soda, baking powder, and salt in a separate bowl.

Gradually add the dry ingredients to the wet ingredients, folding gently until just combined.

Carefully fold in the blueberries and blueberry preserves.

Cover the dough with plastic wrap and refrigerate it overnight.

Once chilled, scoop and roll the dough into balls, coating each with cane sugar.

Bake in the preheated oven for 15-18 minutes or until edges are golden.

Let the cookies cool on the baking sheet for about 10 minutes before transferring to a cooling rack.