In a medium bowl, whisk together the flour, baking soda, baking powder, salt, cinnamon, and pumpkin pie spice.
In a separate large bowl, whisk together the pumpkin purée, granulated sugar, brown sugar, oil, eggs, vanilla extract, and milk until smooth.
Add the dry ingredients to the wet ingredients and stir gently until just combined. Do not overmix.
Spoon the batter into the prepared loaf pan, pressing it gently into all of the harvest details. Smooth the top.
Bake at 350°F for 55–65 minutes, depending on your pan's depth. A skewer inserted into the deepest pumpkin section should come out clean or with a few moist crumbs.