Place the oil and seeds into a 10-inch saute pan and set over medium-high heat. Toast the seeds while constantly moving the pan. You will smell their aroma and hear some of them begin to crackle when they are toasted, 4 to 5 minutes. Transfer the seeds to a small mixing bowl, add the cayenne, cinnamon and salt and stir to combine.
Line a half sheet pan with a silicone baking mat.
Place a 3-quart saucier inside a large cast iron skillet. Add the sugar and water to the saucepan, and cook over high heat, stirring occasionally with a wooden spoon, until it comes to a boil. Stop stirring, cover and cook for 3 minutes. Uncover, reduce heat to medium, and cook until the sugar is a light amber color, approximately 25 minutes. Remove from the heat and stir in the pumpkin seed mixture. This will greatly reduce the temperature of the sugar, so work quickly. Once evenly mixed, pour the mixture onto the prepared half sheet pan. Using an oiled spatula, spread thin. You will have to work quickly when pouring out and spreading the mixture in the pan. Cool completely, approximately 30 minutes, and then break into pieces. Store in an airtight container for up to 2 weeks.
Recipe courtesy of Alton Brown, 2008