Preheat oven to 300 degrees F. Combine pretzels and nuts in a medium heatproof bowl and set aside. Line 2 large baking sheets with parchment paper or alternately grease generously with butter, and set aside.
In a small saucepan over medium heat, combine canna-butter, brown sugar, water, and cayenne. Bring mixture to a boil, stirring constantly. Cook for about 20 seconds. Pour over the pretzels and nuts and toss to combine and evenly coat.
Spread pretzel mixture in a single layer on the prepared baking sheet. Bake for 10 minutes. Stir mixture to break up pieces and return to oven for 15 more minutes.
Let cool slightly before serving. Store for a week or more in an airtight container after cooling completely.