On the "everything flat bread", I smeared a mixture of our favorite Spanish olive oil and my wife's strained yogurt (Greek yogurt) with chopped fresh dill. I seasoned it with salt and freshly cracked black pepper. I then placed a skinned and sliced Campari tomato on top. Finally, I topped the stack with the filet of mackerel.
This was rather good. The mackerel was neutral tasting. Despite being canned in olive oil it was not oily and the usual strong favor was not prominent. The Greek yogurt with olive oil is as good or better than sour cream (our home made creme fraiche could have been better, though).