This turned out to be much more Negroni riff than Margarita; but as a stand-alone cocktail it was very tasty.
Note - I originally made this with 20ml...
I really like Negroni variants, and this one is excellent. Tequila and Campari are the key flavors, but the Cointreau and port are adding flavor and dimension, and the lime cordial is a subtle but important element of the flavor backbone.
Matt