Preheat the oven to 300°F and cover a rimmed baking sheet with aluminum foil. Set aside.
In a medium mixing bowl, toss the pumpkin seeds with the butter to coat evenly. If the seeds are recently rinsed, blot with a paper towel before coating.
Stir together the salt, garlic powder, onion powder, paprika and red pepper in a small bowl. Sprinkle the spice mixture over the buttered seeds, tossing to evenly coat.
Lay the pumpkin seeds in a single layer on the prepared baking sheet, roasting for 20 minutes. Turn and roast for an additional 20 minutes.
Eat warm or at room temperature. Store at room temperature in an airtight container.
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