Line a half sheet rimmed baking tray with a silicone baking mat. Set aside.

In a large saucepan, stir together granulated sugar, corn syrup, and water. With a pastry brush, brush down sides of pan with water.

Cook over medium heat, without stirring, until syrup turns light golden brown and resembles honey, about 12-15 minutes.

Stir in the butter and allow it to melt.

With a heat proof spoon, stir in the pepitas until fully incorporated.

Stir in the baking soda, fine sea salt, ground cinnamon, and ground cayenne pepper. Mixture will bubble and splatter.

Pour out onto prepared tray. Allow to cool completely at room temperature, about 1 hour.

With your hands, break the slab into pieces.

Store pumpkin seed brittle in an airtight container at room temperature for up to 2 weeks.