An orange question

When out in Athy the other afternoon, we managed to score some plaintain from the local African grocery. This is a good thing, and calls for a brief swerve into something Caribbean for dinner.

So the breaded version of Cuban steak (with twice-fried plantain on the side) is on the menu. One thought, though. The recipe calls for the steak to be marinated in “sour orange juice”. Other similar recipes give a workaround for faking it with orange and lime juice. No problem: we have those.

The question, though, since I have an interest in rare/unusual citrus: what’s the standard source fruit for “sour orange juice” in Cuba? A Seville, perhaps? Anybody have an idea?