layered mackerel curry

[crisgal]

As per my previous post, i have a load of mackerel and been thinking what to do with it.
i once went to my friend's house, and they were just finishing what they called'mackerel curry'.
It was in a shallow dish, and apperaed to be layered with sliced onions, and had a tomato based sauce. I was offered just a taste on a spoon as we were going out.
it was absolutely delicious, and i asked for the recipe. The family members all said - you're joking, mum won't tell a living soul!
I have searched on the internet but there are hundreds of mackerel recipes.
Does anyone have any idea how it could be made?