This slimy specialty is from Ciudad Obregon, Sonora: Aleta de atun, or "tuna fin" that's been slow boiled for hours along with string ray meat. (The tuna is the black stuff on top.) When it comes out glistening like clamshells in the afternoon sun, you know it's ready. Found in Tucson at Baja Mar - Mariscos y Cahuamanta with several locations including the northeast corner of Oracle Road and Miracle Mile.
Tuna fin tacos
Add this oddity to your food bucket list: a Taco Super with manta ray, octopus and glutinous black tuna fin, $3.75.

