Roast the yam on a foil-lined baking sheet at 400ºF for about 45 minutes, until it is fork-tender and its skin is slightly caramelized. Let cool, then peel. Mash the flesh with a fork; you should have about 1 cup of puree. Reduce the oven temperature to 350ºF. Spray an 8½" x 4½" loaf pan with a neutral-flavored baking spray, and line the bottom with a strip of parchment paper.
Heat the teaspoon of oil and pepitas in a skillet just wide enough to hold the pepitas in a single layer. Cook until they are lightly browned and make popping noises. Remove from the heat. Add the paprika and allspice. Stir, and let cool in the pan.
In a small bowl combine the flour, baking powder, and salt, gently aerating by stirring with a spatula. In a separate bowl mix together the lightly beaten eggs with the buttermilk, brown sugar, remaining 1⁄3 cup canola oil, molasses, and mashed yam. Add the seasoned pepitas along with any remaining oil in the pan. Fold the flour mixture into the buttermilk mixture; stir just to combine—do not overmix.
Spread the batter evenly in the prepared loaf pan. Bake for 45 to 50 minutes, or until a toothpick comes out clean and the bread springs back to the touch. Remove from the pan as soon as possible, and let cool on a rack. This bread should be allowed to cool for at least 45 minutes before being cut. The loaf needs that time to allow the structure to set; it will seem doughy or underbaked if cut too early.