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

In a large mixing bowl, beat together the unsalted butter, granulated sugar, and light brown sugar until light and fluffy, about 2-3 minutes.

Add in the eggs one at a time, mixing well after each addition, then pour in the cake batter extract and mix until completely combined.

In a separate bowl, whisk together the baking powder, salt, and all-purpose flour. Gradually add this to the wet ingredients and mix on low speed until combined.

Fold in the rainbow sprinkles gently using a spatula.

Drop rounded balls of dough onto the baking sheets, spacing them about 2 inches apart, and lightly flatten each ball.

Bake in the preheated oven for 13-20 minutes or until the edges are golden brown and the centers are soft.

Allow the cookies to rest on the sheets for about 5 minutes before transferring to wire racks to cool completely.

While the cookies cool, prepare the frosting by beating together the unsalted butter and powdered sugar until light and fluffy, then add heavy cream to reach the desired consistency.

Frost the cooled cookies and sprinkle with additional rainbow sprinkles for decoration.