1 good-sized zucchini (about 12 ounces)
1 cup flour
1/2 cup whole wheat pastry flour (or just use additional flour)
1 teaspoon baking powder
1 teaspoon baking soda
1 teaspoon coarse salt
3/4 cup medium-grind cornmeal
1/2 cup (1 stick) unsalted butter, plus additional for greasing pan
1/2 cup buttermilk
2 large eggs
1/3 cup sugar, plus additional coarse sugar for sanding the top
Preheat your to 350° Fahrenheit. Butter and flour a loaf pan, and set aside.
Trim the ends off the zucchini, and slice a half-dozen whisper-thin slices off to reserve as garnish. Grate the remaining zucchini on the coarse holes of a grater, then set aside in a colander to drain while you prepare the rest of the recipe.
In a large bowl, sift together the flours, baking powder, baking soda, salt and cornmeal. Set aside.
Melt the butter in a small saucepan over medium-high heat. Continue cooking until butter solids at bottom of pan turn golden brown, about 3 minutes, then pour out into a medium bowl. Let cool slightly, then pour in the buttermilk, whisking to help cool the butter and take the chill off the buttermilk. Add the eggs and sugar, and whisk well to combine. Give the zucchini a quick press in the colander to release any liquid, and stir into the bowl as well.
Gently fold the dry mixture into the zucchini mixture, stirring until *just* combined (the mixture will be quite thick). Pour into your prepared pan, and smooth the top. Gently lay the reserved zucchini slices in a row down the top, then sprinkle generously with coarse sugar. Bake until golden and a tester comes out clean, ~45 minutes to an hour. Let cool in pan for 15 minutes, then turn out onto a rack and cool fully before slicing.