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

In a large mixing bowl, combine softened butter, granulated sugar, and brown sugar. Beat on medium speed for 2-3 minutes until light and fluffy.

Add in one large egg and vanilla extract, mixing until fully incorporated.

Gradually mix in one cup of all-purpose flour until a thick dough forms.

Fold in approximately two cups of Fruity Pebbles cereal gently with a spatula.

Using a cookie scoop, drop mounds of dough onto the prepared baking sheets, spacing them 2 inches apart. Bake for 10-12 minutes.

Cool the cookies on the baking sheets for a couple of minutes before transferring them to wire racks. Frost once cooled.