Light the coals first. Build a fire and let it burn down to steady coals, or light charcoal briquettes in a chimney until ashed over, about 20 minutes. While they heat, mix the batter. For a 12-inch Dutch oven at about 350°F, plan on 24 coals in total: 8 underneath and 16 on the lid.
Whisk the wet ingredients. In a large bowl, whisk the pumpkin puree, eggs, oil, both sugars, and vanilla until smooth and the sugar is no longer gritty, about 1 minute.
Add the dry ingredients. Sprinkle the flour, baking soda, salt, cinnamon, nutmeg, ginger, and cloves over the wet mixture. Stir with a spatula just until no dry flour remains. Fold in the nuts, if using. A few small lumps are fine; overmixing makes quick bread tough.
Line the pot. Grease a 12-inch camp Dutch oven with legs and a flanged lid, and line it with a parchment sling if you have one. Scrape in the batter and smooth the top.
Set the coals and bake. Set the oven over 8 coals and arrange 16 coals on the lid. Bake for 55 minutes, rotating the oven a quarter-turn one way and the lid a quarter-turn the other way every 15 minutes, so no one side takes all the heat. Start checking at 50 minutes.
Test for doneness. The loaf is done when the top is domed and set and a toothpick in the center comes out clean or with a few moist crumbs, with no wet batter. For the surest check, the center should read 200°F to 205°F on an instant-read thermometer. If the top is browning too fast, move 2 or 3 coals off the lid.
Cool before slicing. Lift the lid and let the loaf cool in the pot for 15 minutes, then lift it out with the parchment and cool on a rack until it slices cleanly. Warm is wonderful; hot crumbles.
