There’s everything to like about this dish. Thin slivers of just-cooked beetroot doused in a simple red wine vinegar dressing, crisp apple, fresh pan fried mackerel and finished with some nutty, leafy and tangy adornments. It’s a simple recipe for success that I can’t believe has sat in my recipe notes, remaining unpublished for so long. I wrote this recipe in the summer of 2014 and was instantly taken with it. It was made few …