Is there any way to "Salt" unsalted cashew pieces?
You may have luck just tossing them in popcorn salt. Popcorn salt is ground much finer than regular salt, and should stick to the surface much easier than the larger grains in table salt or kosher salt. If you don't have popcorn salt, you can start with kosher salt and pulverize it into a fine powder in a food processor, spice/coffee grinder, or mortar and pestle.