Clean the mackerels of their heads and guts. Salt on both the outside and inside and sprinkle with crushed cumin, black pepper directly into the greased tray, in which you will bake them in.
Sprinkle them with crushed garlic, add the white wine. Leave them to sit for 1-2 hours. Then top lightly with oil, arrange lemon slices, cover with foil and put them to bake in a moderately heated oven.