Preheat your oven to 350°F and grease a standard loaf pan with nonstick spray. Line the bottom with parchment paper for guaranteed easy removal after baking completes.

Whisk together flour, baking soda, baking powder, pumpkin pie spice, and salt in a medium bowl. Set this mixture aside; do not add wet ingredients yet, because premature mixing develops gluten.

In a large bowl, combine pumpkin puree, both sugars, eggs, oil, sour cream, and vanilla extract. Whisk until completely smooth and emulsified, about 1 minute of vigorous mixing.

Fold the dry ingredients into the wet mixture using a rubber spatula with 12-15 gentle strokes. Stop when just combined; this moist pumpkin spice loaf recipe depends on minimal mixing to prevent toughness.

Fold in chopped pecans, then pour batter into the prepared loaf pan. Tap the pan twice against the counter to release air bubbles, then smooth the top with an offset spatula.

Bake for 48–52 minutes until a toothpick inserted in the center comes out with just a few moist crumbs attached. The top should turn deep golden brown, not pale.

Cool in the pan for 15 minutes before turning out onto a wire rack. Complete cooling takes 3 hours; resist slicing until fully set, because warm bread crumbles.