Dry toast the pepitos in a skillet until they start to pop.
In a saucepan, combine heavy cream, pumpkin puree, spices and salt. Get this mixture quite warm, but not boiling. Set aside.
In a second heavy bottomed pan, with sides at least 4 inches high, combine the sugar, both syrups and water. Stir until the sugars are melted. Bring to a boil. Then slowly add the cream and pumpkin mixture, and slowly bring this mixture back to a light boil. Stir constantly for 15-20 minutes until the sauce becomes thick.
Pull the caramel sauce off the heat and stir in the butter and lemon juice. Stir vigorously so that butter is fully incorporated.
Store in an airtight container in the refrigerator and reheat in a double broiler before serving. (You could also reheat in the microwave in 15 second intervals until warm)
You can use a less caramel depending on how sweet you like your caramel popcorn.