Gather all your ingredients: all-purpose flour, baking powder, baking soda, salt, pumpkin pie spice, butter, brown sugar, eggs, vanilla extract, canned.
Preheat your oven to 350°F (175°C). Grease a 10-cup bundt pan with butter and lightly dust with flour to prevent sticking.
In a bowl, sift together 2 cups of all-purpose flour, 1 teaspoon of baking powder, 1/2 teaspoon of baking soda, 1/2 teaspoon of salt, and 2 teaspoons.
In a large mixing bowl, cream 1 cup of softened butter with 1 1/2 cups of packed brown sugar until light and fluffy, about 3-4 minutes.
Add 3 large eggs, one at a time, to the butter-sugar mixture, beating well after each addition. Mix in 1 teaspoon of vanilla extract.
Mix in 1 cup of canned pumpkin puree until well combined. This adds moisture and flavor to the cake.
Alternate adding the dry ingredients and 1/2 cup of buttermilk to the batter, beginning and ending with the dry ingredients. Mix until just combined.
Pour the batter into the prepared bundt pan, spreading it evenly with a spatula. Tap the pan gently on the counter to remove air bubbles.