Preheat your waffle iron according to manufacturer's instructions. In a small bowl, mix together the 1/2 cup sugar and 2 tablespoons cinnamon for the coating, then set aside.
In a large mixing bowl, whisk together the flour, 2 tablespoons sugar, baking powder, baking soda, and salt until evenly combined with no lumps.
In a separate medium bowl, whisk together the buttermilk, eggs, 1/3 cup melted butter, and vanilla extract until smooth and well blended.
Pour the wet ingredients into the dry ingredients and gently fold together with a spatula until just combined. Small lumps are fine — do not overmix. Let the batter rest for 5 minutes while the waffle iron finishes heating.
Lightly brush the preheated waffle iron with melted butter, then sprinkle about 1 tablespoon of the cinnamon sugar mixture directly onto the iron surface before pouring batter.
Pour about 2/3 cup batter (or amount recommended for your waffle iron) onto the center of the iron. Close the lid and cook for 3-5 minutes, until the waffle is golden brown and steam has mostly stopped escaping.
Carefully remove the waffle and immediately sprinkle both sides with additional cinnamon sugar while still hot. Place on a wire rack in a 200°F oven to keep warm and crispy while you cook the remaining waffles.
Repeat the process with remaining batter, brushing the iron with butter and sprinkling cinnamon sugar before each waffle. Serve immediately with your favorite toppings.