Trim the ragged ends of the rhubarb. If the large stalks look tough or fibrous, peel and chop them into chunks about an inch long, then put them in a 3-quart saucepan with the sugar, zest, juice and salt.
Cook over medium heat until the rhubarb has broken down into a rough puree, about 20 minutes. Don’t use the food processor—the look of the textured threads of rhubarb is appealing just as it is.
Chill well. Serve cold with cream poured over, turn into a rhubarb fool by folding into whipped cream or use it to fill a prebaked tart shell.