Melt the butter in the microwave and place in a large mixing bowl.
Add the brown sugar and white sugar to the butter and stir until well combined.
Mix in the vanilla and egg until just combined.
Add the flour, baking soda, and salt and mix until just combined.
Stir in the Fruity Pebbles by hand, reserving a few to press onto the tops of the cookie dough, if desired.
Portion into 12 balls of dough and place on a large baking sheet.
Bake for 10 minutes exactly. Cookies will still be slightly underdone when you remove them from the oven. Do not overbake.
Let sit on baking sheet for 5 minutes before removing to a cooling rack or eating.
Video
Notes
Cookies should still look underdone when you remove them from the oven. They'll finish cookie and set up as they cool on the hot baking sheet.Store cookies in an air tight container for 3-4 days. They will stay nice and soft, so long as you don't overbake them.