In a food processor fitted with a metal blade, working in batches, finely chop cucumbers, transferring batches to a glass or stainless steel bowl as they are completed. Sprinkle wit picking salt and turmeric. Add water, cover, and let stand in a cool place for 2 hours. Transfer to a colander placed over a sink and drain thoroughly. Rinse with cool water and drain thoroughly again. Using your hands, squeeze out excess liquid.
Meanwhile, prepare canner, jars, and lids
In a large stainless steel saucepan, combine drained cucumbers, onions, sugar dill seeds and vinegar. Bring to a boil over medium-high heat. Reduce heat and boil gently, stirring occasionally, until slightly thickened and vegetables are heated through, about 10 minutes.
Ladle hot relish into hot jars, leaving ½ head space. Remove air bubbles and adjust headspace, if necessary, by adding hot relish. Wipe rim. Center lid on jar. Screw band down until resistance is met, then increase to fingertip-tight.
Place jars in canner, ensuring they are completely covered with water. Bring to a boil and process for 15 minutes. Remove canner lid. Wait 5 minutes, then remove jars, cool, and store.