Mackerel is oily enough to need no fat added and unforgiving enough to be ruined by five extra minutes; eighteen at 200 °C and take it out. Lemon slices go inside the fish, not on top, where they only steam the skin.
It did not make it into the plan for these seven days.
The method above is what decides the dish, not a step-by-step recipe. The link runs a web search on the name: this page has no vetted sources of its own, and will not invent any.