In a medium bowl, combine 2 cups of all-purpose flour, 1 teaspoon of baking powder, 1/2 teaspoon of baking soda, and 1/4 teaspoon of salt. Whisk until well blended.

In a stand mixer, cream together 1/2 cup of unsalted butter and 1 cup of granulated sugar on medium speed until light and fluffy, about 3-4 minutes.

Add 1 cup of sourdough starter, 1 egg yolk, 2 tablespoons of lemon juice, 1 tablespoon of lemon zest, 1 teaspoon of vanilla extract, and optional yellow food coloring. Mix on low until just combined.

Gradually add the dry ingredients to the wet mixture, mixing on low just until the dough forms.

Cover the mixing bowl with plastic wrap and refrigerate the cookie dough for at least 2 hours.

Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

Use a cookie scoop or two tablespoons to form 1-inch balls of dough. Roll in powdered sugar until fully coated.

Place the sugar-coated dough balls about 2 inches apart on the baking sheet. Bake for 11-13 minutes, until edges are set and centers are gooey.

Remove cookies from the oven and allow to cool on the baking sheet for at least 5 minutes before transferring to a wire rack.