Generously spray a 9x13 or 8x8-inch pan with non-stick cooking spray and cover with parchment paper, leaving a 2-inch overhang on at least two of the sides. \nAdd the butter to a medium sauce-pot and melt over medium-low heat. Once melted, add the marshmallows, corn syrup, vanilla, salt and Belize spice. Stir continuously until the marshmallows are almost completely melted. Add cereal and grapefruit zest and stir vigorously until all of the cereal is well coated. \nPour mixture into prepared pan and pat down firmly using well-greased hands or greased wax paper. Allow to cool completely at room temperature, about 1 hour. \nUsing the parchment paper overhang, remove the treats from the pan. Cut into squares and serve.