Step 1

Preheat oven to 350°F and line an 8-inch square metal baking pan with parchment paper; spray lightly with nonstick spray. Whisk together melted butter, sugar, brown sugar, and vanilla in a medium bowl until combined. Whisk together flour, baking soda, salt, and cinnamon in a medium bowl; add to butter mixture and fold in until incorporated. Press dough evenly into bottom of prepared pan. Bake crust for 22 minutes, until tops and edges are golden and set. Transfer to a wire rack and cool for 15 minutes.

Step 2

For the topping, combine butter and macadamia nuts in a heavy saucepan over medium-high heat and cook for 3 minutes, stirring constantly, until mixture is foamy and fragrant. Add salt, brown sugar, maple sugar, and maple syrup to pan. Boil, stirring constantly, for 2 minutes. Quickly pour topping over crust and tilt pan to coat crust evenly. Cover pan and chill in the refrigerator until completely set, about 2 hours.

Step 3

When ready to serve, carefully lift parchment and place bars on a cutting board; cut into bars with a sharp knife. Store leftover bars in an airtight container at cool room temperature or in the refrigerator; let stand at room temperature before serving.