Mackerel baked in the oven

• 1 kg freshly frozen mackerel
• 0.5 kg onion
• 50 grams of mayonnaise
• 50 grams of ketchup
• 0.5 teaspoon dried basil
• 0.5 teaspoon dried parsley
• salt and pepper to taste

Cooking:

1. Cut mackerel into pieces.
2. Peel the onion and cut into rings.
3. Mix pieces of mackerel and onion with ketchup and mayonnaise, salt, pepper and add spices. Leave to marinate for 2 hours in the refrigerator.
4. Put parchment on a baking sheet.
5. Preheat the oven to 180 degrees.
6. Put prepared pieces of mackerel on a baking sheet, and put onions between them.
7. Bake for about an hour until done.