Today’s Cocktail O’Clock comes from Firefly in D.C., which somehow fits everything we like about summertime drinking — tequila, grapefruit juice, fresh mint, lime — into one cocktail. Even though we just recently hated on jars, the Tranquilo is one summer cocktail we’d take for a spin.

5 mint leaves, muddled
3 parts fresh grapefruit juice
2 parts Herradura Reposado tequila
1 part Cointreau
1 squeeze of lime juice

Shake and serve in a mason jar, garnish with a mint sprig and a slice of grapefruit.

Find more summer cocktail ideas in Endless Cocktails.

(Photo: Dakota Fine)