With a mandolin or sharp knife, slice cucumbers 1/4-inch thick. Combine sliced cucumbers and salt in a medium sized bowl. Cover and chill for 1 -2 hours. Drain cucumbers and rinse with cold water. Drain well and return to bowl. Add sliced onions and toss gently.

In a medium saucepan combine vinegars, sugars, mustard seeds, peppercorns, celery seeds, and turmeric. Bring to a boil and simmer over medium heat, stirring until the sugar dissolves.

Pour hot vinegar mixture over the cucumbers, let stand at room temperature for 1 hour. With a slotted spoon transfer the pickles and onions to glass container(s). Pour the pickling liquid evenly over the pickles until jar(s) are full. Store in refrigerator up to 1 month.