Cut the mildest possible herring into bite-sized pieces. Cut the onions into fine rings. Skin, core and dice tomatoes and peppers. Cut the olives into slices.
Mix everything together, add herbs as desired, squeeze in the garlic. Now mix with vinegar and oil and season with pepper and (carefully) salt. Let it flow well.
Tastes good with baguette or jacket potatoes. Also delicious: add a small chilli pepper, finely chopped!