Make a simple syrup by adding the sugar and 1/2 cup water to a very small saucepan and heating over low heat until all of the sugar is dissolved. Transfer to a container and allow to cool completely in the fridge.
Grab the bag of frozen peaches and the lemon zest and add them to a blender with the cold simple syrup; blend until smooth. Place the blender pitcher in the fridge until you need it.
To serve, pour some puree into a champagne flute and top off with very cold champagne or sparkling wine.