Lightly grease pan. I use an 8x8 or 9x9 for thicker treats, use a 9x13 pan for thinner. Set aside
Melt butter in a saucepan big enough for all ingredients over medium/medium-low heat.
Add in marshmallows, stirring frequently until melted.
Add in vanilla and zests and fully mix into melted marshmallow and butter.
Turn off and remove saucepan from heat, add in cereal and mix until coated.
Dump mixture into prepared pan and lightly press into an even layer. Using a butter wrapper or a greased piece of wax or parchment paper can help you flatten out the top.
Let set for about 30 minutes before cutting to allow marshmallow to cool. Enjoy!