Preheat the oven to 350 degrees and line a baking sheet with parchment paper.
Stir together the flour, baking powder, and salt in a small bowl.
In a larger bowl, beat the softened butter and sugar until light and fluffy.
Add the egg and vanilla extract to the butter mixture and mix until smooth.
Gradually add the dry ingredients to the wet mixture and stir until a dough forms.
Fold in the rainbow sprinkles until they are evenly distributed.
Scoop rounded tablespoons of dough onto the prepared baking sheet, spacing them a few inches apart.
Gently press three or four candy eyes into the top of each dough ball before baking.
Bake for 10 to 12 minutes until the edges turn lightly golden.
Cool the cookies on the baking sheet for a few minutes, then transfer them to a wire rack.