1. Melt butter in a small saucepan over medium heat. Add pumpkinseed kernels and next 4 ingredients (through red pepper); cook 3 minutes, stirring frequently. Set aside.
2. Combine sugar, corn syrup, and 1/4 cup water in a medium, heavy saucepan over medium-high heat; bring to a boil, stirring just until sugar dissolves. Cook until a candy thermometer registers 335°. Remove pan from heat; add pumpkinseed mixture and baking soda. Working quickly, spread mixture in a thin, even layer on a baking sheet lined with parchment paper; let stand until set. Break into pieces.