Preheat oven to 350 degrees.
In a small pan over medium heat, melt the butter while stirring occasionally. Cook the butter until it begins to turn an amber color and have a nutty aroma. Remove the browned butter to a large mixing bowl and set aside to cool.
Spread the macadamia nuts on a parchment lined baking sheet and bake at 350 degrees for 10 minutes. Transfer the nuts to a cutting board and coarsely chop. Set aside.
Cut a length of parchment paper to fit a 8x8 inch baking dish allowing the paper to come up to the top of both sides of the pan. Cut another sheet to fit in the opposite direction also trimming at the top of the pan. Spray the parchment lightly with cooking spray. Set aside.
Whisk together 3/4 cup of flour, baking soda and salt together in a small mixing bowl. Set aside.
In the bowl with the browned butter add the brown sugar and stir using a wooden spoon or spatula until blended. Add the egg and mix until it lightens in color and is smooth. Blend in the rum and vanilla and mix just until incorporated. Fold in the dry ingredients just until combined. Do not over-mix.
Place the white chocolate chips in a small bowl and toss with the remaining 1 tablespoon flour. Add the chocolate chips (with flour), coconut and macadamia nuts to the batter. Fold in gently. Spread the batter evenly in the prepared pan.
Bake at 350 degrees until the top is shinny, cracked and light golden brown, about 22-24 minutes. Do not over-bake. Blondies should be chewy, not crunchy.
Cool the blondies in the pan then lift out using the parchment paper. Transfer to a cutting board and slice into bite sized squares. Enjoy!