Cut the cucumbers and onions into 1" chunks.
Add to a large food processor and pulse into small pieces, about ¼" pieces.
Add the cucumbers, onions and pickling salt to a bowl, stir well, cover and refrigerate overnight.
Squeeze liquid from the mixture, then add the cucumbers and onions to a dutch oven.
Add the vinegar, sugar, turmeric and celery seed.
Whisk well, then bring to a simmer and cook for 15 minutes on medium heat.
Whisk the water and cornstarch together into a slurry, then add it to the relish.
Stir well and continue to cook until thickened to a normal relish consistency, another 15-20 minutes.
Serve over hot dogs or your favorite picnic foods.
Store in a tightly closed container in the refrigerator for up to 2 weeks or process for canning for long term storage.
