Line baking sheet with parchment paper and grease well with butter.
Combine the sugar, honey and water in a heavy-bottomed saucepan and bring to a boil over high heat. Without stirring, Cook until reaches "hard crack", about 300F on a candy thermometer, while occasionally brushing the inside of the pot with cool water. This will take about 7-9 minutes, and the sugar will turn a deep amber color.
Remove from heat. Using a wooden spoon, stir in the salt and macadamia nuts. Carefully add butter, baking soda, and vanilla; it will immediately foam. Working quickly, spread brittle onto the prepared baking sheet. Allow to set completely before cracking into pieces.