Step 1: Preheat your oven to 350°F (175°C) and thoroughly grease and flour a 10-cup bundt pan.
Step 2: In a medium bowl, whisk together the flour, ground cardamom, baking powder, baking soda, and salt.
Step 3: In a large bowl, cream the softened butter and sugar until the mixture is light and fluffy, about 3-5 minutes.
Step 4: Add the eggs one at a time, beating well after each addition, then stir in the pumpkin puree and vanilla extract.
Step 5: Gradually add the dry ingredients to the wet ingredients, alternating with the sour cream, starting and ending with the flour mixture.
Step 6: Pour the batter into the prepared bundt pan and smooth the top with a spatula.
Step 7: Bake for 55-60 minutes, or until a wooden skewer inserted into the center comes out clean.
Step 8: Allow the cake to cool in the pan for 15 minutes before carefully inverting it onto a wire rack to cool completely.