Place the sugar cube into the bottom of a rocks glass. Shake the bitters over the sugar and then pour in the water. Muddle until the sugar is mostly dissolved, this may take a minute or two.
Add some ice to the glass. Pour in the bourbon and gently stir.
Gently squeeze the orange peel in half over the glass to express the orange oils onto the drink. Then drop the peel into the glass along with a maraschino cherry for garnish.
Notes
You want to use a full piece of orange zest, removing as much of the pith as possible using a pairing knife. This will make it easier to express the oils and not leave a bitter taste in the cocktail from the pith.
If you don’t have sugar cubes, you can use 1 teaspoon of sugar and muddle it with the bitters and water.