Step 1

Combine fruit, water and sugar to taste in a Dutch oven; add citrus zest and juice if using. Bring to a boil over high heat. Reduce heat to maintain a lively simmer and cook, mashing the fruit and stirring occasionally at first and then often as it thickens, until the mixture is very thick, 20 minutes to 1 hour (depending on the type of fruit). To test doneness, put a spoonful of fruit butter on a plate. If no liquid seeps from the edges, it's done. Return to a simmer to thicken more if necessary. For very smooth fruit butter, puree in a food processor or blender, then strain and push the mixture through a sieve before storing.

Step 2

If freezing or refrigerating, ladle the fruit butter into clean canning jars to within 1/2 inch of the rim. Wipe rims clean. Cover with lids. Let the jars stand at room temperature until cool before refrigerating or freezing. Or process in a water bath to store at room temperature (see Tip).