Working in batches, add a few handfuls of the citrus rinds to the bowl of a food processor and pulse until finely chopped. Transfer the processed citrus rinds to a large Dutch oven or heavy bottomed pot add the water or citrus juice.

Set the pot over medium- high heat and bring to a boil, about 20 minutes, stirring occasionally. Continue boiling for 10 minutes, stirring occasionally. Stir in the sugar, any flavorings, if using, add the salt. Place a candy thermometer in the pot, if you have one. Reduce the heat to medium.

Continue boiling the mixture, stirring frequently, until it reaches 215F. To 220F, about 45 minutes. At this point, the liquid should be thick and syrupy and the pieces of rind should appear transparent.

From here, the hot marmalade can be transferred to jars and kept refrigerated for up to 3 months, or it can be placed in sterilized 8- ounce canning jars and processed in a water Bath for 12 minutes (see pickling page 308, for sterilizing and canning instructions.