Add all ingredients to a cocktail shaker and shake with ice to chill.
Fine-strain through a mesh strainer over fresh ice into a cayenne-chili salt-rimmed rocks glass.
Garnish with orange zest - or a drizzle of citrus.
* Blackberry shrub: Combine equal parts blackberries, cane sugar and red wine vinegar in a blender, blend until liquefied, then strain out solids.
** Cayenne-chili syrup: Combine 1 cup sugar, one cup water, 1 teaspoon chili powder, 1 teaspoon cayenne in a saucepan and bring to a simmer. Once the desired flavor is achieved, strain out solids. Alternately, use .25 oz simple syrup, a slice of cayenne or other hot pepper, and a pinch of chili powder.
*** Cayenne-chili rim: 4 parts kosher salt + 1 part chili powder + 1 part cayenne