Shed the sardines, gut them, rinse, pat dry and fry them in portions. Place on kitchen paper and let cool down. For the marinade, peel and cut the onions into rings, peel and core the tomatoes and cut into pieces, finely chop parsley and garlic. Briefly heat the olive oil in a pan and first lightly brown the onions in it, then add the garlic, bay leaf, tomato and parsley, add a little salt and deglaze with white wine and vinegar. Cook for 5 minutes and let cool down. Put the sardines in a bowl, season with salt, pepper and sprinkle with paprika.
Pour the marinade over it and let it steep in the refrigerator for 2 days.
Before serving, garnish with onion rings and parsley and pour a little marinade over them in portions.