Peel and cut the onions into thin slices, cutting the onion in the middle and then vertically. Put the butter in a large pan to melt and put the fire as low as possible. Place the onions in the pan and leave about 30-40 minutes stirring intermittently to avoid burning underneath. They will begin to soften and they will make all the sweetness so we do not need sugar. Somewhere in the middle add the thyme and stir again. Finally, remove them from the fire and pour paprika, salt, pepper and serve.