For the Preserved Orange:
Combine the salt and the sugar and mix thoroughly. Pack the orange slices in the mixture and transfer to a chilled area for three weeks. Check daily to remove any liquid that accumulates.
For the Cocktail:
In a shaker, combine the tequila, bitters, and orange juice, and ice. Shake and strain into a Pilsner glass filled with ice. Add maraschino juice and top with beer. Garnish with preserved orange.