In a mixing glass, combine the bitters, sugar and 1 teaspoon of water. Stir well to dissolve the sugar.
Add the ice and bourbon and stir well to chill.
Strain into a rocks glass over one large, single ice cube.
Twist an orange peel over top the glass to express the citrus oils, then drop it into the glass. Add a cherry to garnish, if desired.
Video
Notes
I recommend using a Y peeler or vegetable peeler for a large strip of zest. This will easily cut off a wide strip that is thin and without the white pith.