Preheat waffle maker on medium-high heat. Preheat oven to 200°F (93°C). Place a wire rack on a baking sheet; set aside.

In a large bowl, preferably with a pour spout, whisk together the flour, baking powder, cinnamon, and salt. Set aside.

In another large bowl, whisk together the melted butter, eggs, and brown sugar. Whisk in the buttermilk and vanilla until combined. Pour the wet ingredients into the dry ingredients, and then whisk gently until combined. Do not over-mix. Some small lumps are OK.

Grease the preheated waffle maker (I use nonstick spray). Pour about 1/3 cup of the batter into each well of the waffle maker (could be more or less, depending on the size of your waffle maker) and close the lid. Cook the waffles until crisp, about 4–5 minutes. (Follow the cooking instructions for your waffle maker.) Transfer the cooked waffles to the wire rack and keep warm in the preheated oven as you cook the rest. Repeat to cook the remaining batter.

Serve the waffles immediately with your choice of toppings.