Onion and potatoes should be peeled and sliced. Having the red bell pepper cleaned, sliced, and the seeds removed

Then, sprinkle them with salt to taste, place them on a baking sheet (with a little oil to prevent sticking), and bake for 15 minutes at 180°C. So they don't burn on one side, stir them once or twice.

Chop the parsley and garlic. The wine and the tablespoons of olive oil should be combined with them in a food processor, blender, or mixer.

The mackerel fillets should be added to the tray along with the garlic, parsley, and oil mixture when the potatoes are almost done.

Bring the baking sheet inside and bake for 10 minutes at the same temperature.