Rays and skates are interchangeable in the kitchen. "Skate wing" is a term of art in the seafood world; you never know whether you're eating skate or ray. But if you get them yourself, rays are slimy, while skates have smooth skin. Some people like their skate wings on the bone, with the cartilage left in. That's fine, just move it aside on the plate once you eaten it. This is a very simple recipe, so use the finest ingredients you can get: The best butter, the best vinegar, the smallest capers. It makes a difference. I like to serve this with bread and a green thing alongside, in this case my sea bean salad.
Note that prep time does not include optional brine.