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

In a mixing bowl, cream the room-temperature unsalted butter and granulated sugar using an electric mixer until light and fluffy, about 3-4 minutes.

Stir in the vanilla extract if using, folding until evenly distributed.

Gradually add the all-purpose flour, mixing until a soft dough forms, about 1-2 minutes.

Roll the dough into 1-inch balls and place them 2 inches apart on the baking sheet.

Flatten each ball slightly and sprinkle with sugar and optional rainbow sprinkles.

Bake for 10-12 minutes until lightly golden around the edges.

Cool on the baking sheet for about 5 minutes before transferring to a wire rack to cool completely.