Butter the sides of a 9x9 inch square baking dish and line the bottom with parchment paper.
In a large bowl combine the melted butter and brown sugar with a whisk to ensure there are no lumps. Add the egg and vanilla extract and mix well. Add the grated zucchini to the wet mix and stir well to combine.
In a separte bowl, sift together the flours, cinnamon, baking soda, and salt.
Add the dry mix to the wet and combine using a spatula or wooden spoon, being careful to not over mix. Stir in the walnuts.
Scrape the blondie mixture into the prepared baking dish and use a spatula to even out the top.
Combine the remaining tablespoon of brown sugar and teaspoon of cinnamon, using your fingers to work them together. Sprinkle the cinnamon sugar mixture over the top of the blondies in an even layer.
Place in the oven and bake for 30 minutes. There should be a few bits of moist batter clinging to a tester when they're done — be mindful to not over bake these, as they should be more chewy than cakey.
Cool on a wire rack until the blondies reach room temperature.
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