Preheat your oven to 350°F (175°C).

In a large mixing bowl, cream together the softened unsalted butter, granulated sugar, and packed brown sugar until light and fluffy.

Add the eggs one at a time, mixing well after each addition, followed by the vanilla extract.

In another bowl, whisk together the all-purpose flour, baking powder, and salt. Gradually add this dry mixture to your wet mixture, blending until just combined.

Scoop about 1 tablespoon of dough and roll it into balls. Roll these cookie dough balls in the colorful sprinkles until they are fully coated.

Place the coated cookie balls on a baking sheet lined with parchment paper, leaving space between them. Create deep indentations in the center of each cookie using your thumb.

Bake in the preheated oven for about 10-12 minutes or until the edges are lightly golden.

Remove from the oven and allow to cool slightly before filling each indentation with lemon curd or a filling of your choice.

Allow to cool completely on a wire rack before serving.