Preheat oven to 400 degrees F. Cut the stem off top of pumpkin as you would if you were carving it; discard. Cut pumpkin in half vertically. Scoop out pulp and seeds with a spoon. Slice pumpkin into 1-inch wide crescents; place each crescent on its side on a baking sheet. Drizzle slices with olive oil, then sprinkle with rosemary, sage, thyme, chili powder and/or cumin, to taste. Sprinkle with salt and pepper to taste.

Bake slices until soft and edges are slightly browned, about 30-35 minutes. Remove from oven and cool completely. Once cooled, scoop out roasted pumpkin flesh from its shell and place in a large bowl. Mash pumpkin into a puree. Reserve 1 cup (save the rest for other tasty savory pumpkin recipes, or to eat with a spoon straight out of the fridge later when you need a midnight snack).

Heat oven to 350 degrees F. Lightly grease a shallow 2 1/2-quart ceramic baking dish with cooking spray and set aside.

In a large bowl, whisk together reserved pumpkin, buttermilk and egg yolks. Set aside.

In a large saucepan over high heat, bring butter and 1 1/2 cups water to a boil; once boiling, remove from heat. In a medium bowl, whisk together cornmeal, brown sugar, baking soda, salt and pepper. Gradually whisk cornmeal mixture into saucepan until well blended. Then, gradually add in pumpkin mixture and whisk until well blended.

In a small bowl, beat egg whites with a hand mixer on high speed just until stiff peaks form, about 3-5 minutes. Gently fold egg whites, one third at a time, into mixture in saucepan. Carefully pour entire mixture into prepared baking dish.

Place baking dish in a roasting pan or high-rimmed baking sheet and place in oven. Pour boiling water into roasting pan or baking sheet until water reaches about halfway up the outsides of the baking dish. Close oven door quickly and bake until spoonbread is golden brown and a toothpick inserted a few inches from the center comes out clean, about 50 minutes to 1 hour. Remove from oven and serve immediately.