-Preheat oven to 350 degrees Fahrenheit (175 degreed Celsius)
Melt 3 tablespoons of butter (in the preheated oven) in either a 10" cast iron skillet or 1 9" x 9" baking pan.
Meanwhile, whisk the flour, cornmeal, salt, pepper, baking powder, baking soda, and brown sugar in a large bowl.
Whisk the milk, vinegar, egg, and pumpkin in a medium bowl.
Pour the pumpkin mixture into the flour/cornmeal mixture and stir with a wooden spoon until just combined. Stir in the chopped sage. Do not overmix.
Spoon the cornbread mixture into the cast iron skillet and spread evenly.
Bake in a preheated oven for 45-50 minutes or until a toothpick inserted in the center comes out clean.
Remove from the oven and immediately brush the entire surface with the remaining melted butter.
-Serving warm is best, but it's also tasty at room temperature.