Preheat the oven to 350°F. Line a 9 inch square metal pan with nonstick foil.
Toast the macadamia nuts on a rimmed baking sheet for about 5 minutes.
Stir the flour, baking powder, and salt together and set aside.
Beat the butter, brown sugar, and granulated sugar with an electric mixer until smooth and creamy. Reduce mixer speed and beat in eggs and extract.
By hand, stir in the flour mixture until just combined. Stir in the butterscotch chips and nuts.
Spread batter into the prepared pan and bake for 45 (check at 35) minutes, until golden brown. Let cool, then lift from pan cut into squares