Preheat oven to 200 degrees. Line a baking sheet with parchment or a silicone baking mat.
In a large sauce pan, combine the washed pumpkin seeds, water and apple cider vinegar. Bring to a boil, then turn heat down so that mixture simmers on the stove top for 10 minutes.
Remove from heat and dump the pumpkin seeds into a strainer, to drain away all the water and vinegar.
Spread the seeds evenly on the baking sheet, and allow to dry in the 200 degree oven... about 30-40 minutes. Check on them once or twice, and shake the pan around a bit to evenly dry them.
Increase oven temperature to 375 degrees.
In a clean bowl, toss the pumpkin seeds with the tablespoon of oil, salt and Parmesan cheese. Mix well to combine,
Again, spread the seeds on your baking sheet and bake for 20 - 25 minutes, shaking pan once or twice during cooking time. Seeds will be nicely browned when finished.