Preheat your oven to 350F and oil or grease a 8.5 x 4.5 x 2.75 inch loaf pan.
In a large mixing bowl, whisk together the flour, baking soda and powder, salt, and pumpkin pie spice.
Combine the non-dairy milk and vinegar and allow them to sit for a moment. In another mixing bowl, combine the oil, sugar, pumpkin puree, and vanilla extract. Whisk in the milk + vinegar.
Make a well in the dry ingredients and pour the wet ingredients into the center. Use a spatula to mix the ingredients into a batter. Don't over-mix: you want there to be no more streaks of flour visible, but a few little lumps are fine.
Pour the batter into your loaf pan. Bake for 20 minutes, then rotate the pan in your oven. Bake for another 20-25 minutes, or until the top of the loaf is domed and set. Allow the loaf to cool for 15 minutes on a cooling rack before removing it from the pan. Allow it to cool for at least two hours before slicing and serving.