Figs don’t need much prep: trim the stem end, quarter them cross-wise, to produce a textured but manageable jam.
Combine the fruit, sugar, lemon juice, and zest, if using, in a mixing bowl. Stir to combine, then cover closely and place in the refrigerator for a few hours or overnight.
Turn the fruit-and-sugar mixture into a saucepan, and rapidly bring to a boil. Stirring constantly, reduce over high heat until the hot jam is thickened, 6 to 8 minutes; then lower the heat to medium, and reduce a few more minutes to the gel point.
Ladle into five prepared ½-pint jars, leaving ¼ inch head space. Seal, and process in a boiling-water bath for 10 minutes.