Preheat the oven to 350.
Line an 8x8 baking pan with foil, leaving a 1 inch overhang on all sides.
In a bowl, combine the flour, baking powder and salt.
Pour the melted butter into a large bowl, and add the brown sugar, maple syrup and honey. Whisk until well blended.
Whisk in the egg and vanilla.
Add the flour mixture, and stir until JUST blended.
Fold in the walnuts.
Pour the batter into the pan, and bake for 25 minutes. Middle should be JUST set.
Let them cool, then remove using the overlapping foil.
Cool on a wire rack, and cut into 16 squares.