Place the blackberries, 1/2 cup of water, sugar, lime juice, and lime zest in a saucepan. Heat until boiling then reduce heat to a simmer. Simmer for 5 minutes or until the berries burst.

Strain the liquid through a fine mesh sieve and discard the solids.

Pour the juice into a quart sized mason jar. Add in the tequila and Triple Sec. Put the lid on and shake. Refrigerate until cooled.

Pour the mixture over top of ice and garnish with blackberries and a lime slice.