Put the raisins or sultanas in a small bowl and cover with just-boiled water. Leave in the water until it is cold and they are needed.
Heat the oil in a medium frying pan over a low heat. Peel and halve the onions lengthways and then very finely slice them, before peeling and thinly slicing the garlic. Add these to the pan and cook very gently for about 15-20 minutes until they are meltingly soft but not at all coloured. Drain the raisins or sultanas and add them to the onions with the vinegar and sugar. Cook for a few minutes more, until the liquid has evaporated, then set aside.
Toast the pine nuts in a dry frying pan over a medium heat, jiggling the pan often to keep the nuts on the move, preventing them from burning in one place. When they have taken on a dark golden hue, allow them to cool on a plate.
Bring a large pan of water to the boil. Wash the chard leaves really well to remove any grit or indignant insects. Split each leaf through the centre and plunge into the boiling water. Cover and cook for 4-5 minutes until tender.
Drain the chard thoroughly in a colander, shaking it to remove any excess water. Really get it as dry as possible. Eaten at room temperature the chard is also delicious, so if need be, rinse it under cold running water first.
Arrange the chard on a serving plate and sprinkle over with some good salt. With your hands, arrange the onion mix over the top, making sure it is all placed well. Sprinkle the pine nuts about. Inspired by a trip to Barrafina, an excellent tapas establishment, I ate a Spanish version of this recipe called 'coca'. Made with spinach and resting upon crispy dough, it was dusted with a little hot smoked paprika. An excellent addition!