In a medium bowl, whisk together the flour, brown sugar, baking powder, grated nutmeg, baking soda and salt. Form a well in the center of the dry ingredients. Separate the egg yolks from the whites and put the whites in a medium bowl. Drop the yolks in the center of the dry ingredients. Add the buttermilk and stir together gently to form a batter. Do not overmix.
Beat the egg whites to medium peaks using a whisk or a hand-held mixer. Add the whipped whites to the batter and, using a rubber spatula, fold them in by gently scooping up some batter from the bottom and folding it over the whites on the top. Rotate the bowl and repeat until just incorporated. Fold in 2 tablespoons melted butter. Add the blueberries and lemon zest, and gently fold in.
Heat a waffle iron and, using a pastry brush or paper towel, lightly coat with melted butter. Cook waffles (using about ⅔ cup batter per waffle) until golden and crisp. Butter the iron between batches as needed.
Serve waffles immediately as they are ready, or keep them warm in a 200-degree oven until ready to serve. Top with warm maple syrup.
