Preheat your oven to 325°F (165°C). Generously grease and flour a 10-inch bundt pan, taking extra care to coat all the crevices.
In a medium bowl, whisk together the flour, baking powder, baking soda, salt, and all spices until well combined.
In a large bowl using an electric mixer, beat the butter on medium speed until smooth and creamy, about 1 minute. Gradually add the sugar and beat on medium-high speed until the mixture is pale and fluffy, about 4-5 minutes.
Add eggs one at a time, beating well after each addition and scraping down the sides of the bowl as needed. Mix in the vanilla extract.
In a separate bowl, whisk together the pumpkin puree and sour cream until smooth.
With the mixer on low speed, add the dry ingredients and pumpkin mixture alternately to the butter mixture, beginning and ending with the dry ingredients (dry → pumpkin → dry → pumpkin → dry). Mix just until combined after each addition.
Pour the batter into the prepared bundt pan, smoothing the top with a spatula. Tap the pan gently on the counter 2-3 times to release any trapped air bubbles.
Bake for 65-75 minutes, or until a wooden skewer inserted into the center comes out clean with a few moist crumbs. If the cake begins to brown too quickly, tent it loosely with aluminum foil after about 45 minutes.
Allow the cake to cool in the pan for exactly 30 minutes, then invert onto a wire rack to cool completely, about another hour.
In a medium bowl, whisk together the powdered sugar, maple syrup, 1 tablespoon of milk, vanilla extract, and salt until smooth. Add more milk, 1 teaspoon at a time, until you achieve a pourable but thick consistency that coats the back of a spoon.
Once the cake is completely cool, drizzle the glaze over the top, allowing it to flow naturally down the sides.