Heat the oven to 325°F and position a rack in the center. Grease an 8.5×4.5-inch loaf pan, then line it with a parchment sling for easy removal.
Bloom the spices: In a small saucepan over low heat, warm the oil with the cinnamon, ginger, nutmeg, and cloves just until fragrant, about 45–60 seconds (do not let it sizzle). Remove from heat and let cool 5 minutes.
Whisk the dry mix: In a large bowl, whisk together the flour, baking soda, baking powder, and salt until well blended.
Build the wet base: In a separate bowl, whisk the sugar, molasses, and eggs vigorously for 60–90 seconds until slightly thickened and lighter in color. Whisk in the pumpkin puree, yogurt, vanilla, and orange zest until smooth. Stream in the cooled spiced oil and whisk to combine.
Combine: Add the wet mixture to the dry ingredients and fold gently with a spatula just until no dry pockets remain. Let the batter rest 10 minutes to hydrate the flour for a more tender crumb.
Bake: Scrape the batter into the prepared pan, smooth the top, and tap the pan once on the counter to release large air bubbles. Bake 60–70 minutes, until a tester inserted near the center comes out clean with a few moist crumbs or the loaf registers 200–205°F in the middle.
Cool and slice: Cool in the pan for 15 minutes, then lift onto a wire rack and cool at least 1 hour before slicing for neat pieces.