Preparation Spray a parchment-lined baking sheet with nonstick spray; set aside. Bring sugar, corn syrup, and 3 tablespoons water to a boil in a medium saucepan over medium heat, stirring to dissolve sugar. Fit saucepan with thermometer and cook until thermometer registers 290°F, 3–4 minutes. Stir in pumpkin seeds, butter, and kosher salt and cook, stirring often, until pale brown and thermometer registers 305°F, 3–4 minutes. Stir in baking soda and cinnamon (mixture will bubble vigorously), then immediately pour caramel onto prepared sheet. Using a heatproof spatula, quickly spread out and sprinkle with sea salt; let cool. Break brittle into pieces. DO AHEAD: Brittle can be made 1 week ahead. Store airtight, layered between sheets of parchment paper, at room temperature.
Preparation Spray a parchment-lined baking sheet with nonstick spray; set aside. Bring sugar, corn syrup, and 3 tablespoons water to a boil in a medium saucepan over medium heat, stirring to dissolve sugar. Fit saucepan with thermometer and cook until thermometer registers 290°F, 3–4 minutes. Stir in pumpkin seeds, butter, and kosher salt and cook, stirring often, until pale brown and thermometer registers 305°F, 3–4 minutes. Stir in baking soda and cinnamon (mixture will bubble vigorously), then immediately pour caramel onto prepared sheet. Using a heatproof spatula, quickly spread out and sprinkle with sea salt; let cool. Break brittle into pieces. DO AHEAD: Brittle can be made 1 week ahead. Store airtight, layered between sheets of parchment paper, at room temperature.