Peel xoconostle with a pairing knife,  slice in half and scoop out and discard center pink portion with seeds.  Place pale green halves in a blender container.  Add sugar and water.  Blend until smooth.

Combine tequila xoconostle mixture and ice in a cocktail shaker.  Shake vigorously for 30 seconds.

Run lime wedge along the edge of two cocktail glasses.  Dip one side in sugar.  Divide cocktail mixture between glasses.  Decorate with cactus flowers and serve.