Preheat oven to 275 degrees F and grease a cooling rack with cooking spray, then place on top of a large baking sheet.
On a large paper towel-lined plate, arrange tomatoes and cover with another paper towel, then press to release juice. Place tomatoes on cooling rack and lightly drizzle with olive oil, then season with salt, and garlic powder.
Bake, checking every 30 minutes, until tomatoes are completely dried out and beginning to crisp up, about 3-5 hours.
Remove from oven and heat broiler. Sprinkle tomatoes with Parmesan, then broil on low until cheese is melty, 1 to 2 minutes.
Let cool, then remove from cooling rack. Garnish with additional salt, pepper and fresh parsley, an other fresh herbs you like or Italian seasoning, if desired, and serve.
Store parmesan chips in an airtight container.