Combine equal parts of chile de arbol and salt on a saucer and use to coat the rim of a Collins glass.
Fill with ice and set aside.
In a shaker, muddle the cucumber, bell pepper and lemon juice.
Add the tequila, agave nectar and bitters, and fill with ice.
Shake, and strain into the prepared glass.
Top with ginger beer and garnish with slices of cucumber and red bell pepper.