This simple version of the Venetian classic (sarde en saor) balances the assertive taste of sardines with a sweet-&-sour marinade flavored with saffron and onions. In summer, I like to just throw the sardines on the grill.
Heat the oil in a sautee pan and cook the onions until they are soft and pale gold. Remove from heat and transfer to a large shallow bowl or pan.
Combine vinegar, sugar, raisins and bay leaf in a small saucepan and crumble in saffron. Heat over low flame, stirring until sugar is dissolved, reducing slightly. Pour over onions. Stir in pine nuts.
Wash and pat sardines dry, then salt and dust with flour. Heat a generous amount of oil in a large skillet and, when hot but not smoking, fry sardines until golden brown, about 2 minutes per side. Don’t crowd pan; fry in batches if necessary.
Place the fried sardines into the marinade and spoon it over so they are well covered. The sardines can be eaten now, with lemon squeezed over, alongside a simple fennel salad and grilled white polenta. Or they can marinate in the refrigerator for a day or two and be served as part of a larger antipasti platter.