Preheat oven to 350° F. Grease and flour a 12-cup Bundt pan (I use Pam Baking spray).
Place 1 cup oatmeal in a small bowl. Pour 1/4 cup boiling water over the oatmeal and stir together. Allow oatmeal and water to sit for 10 minutes.
Add sugar and butter to a large mixing bowl. Beat on low until light and fluffy.
Slowly add the eggs, one at a time, and continue mixing until well incorporated.
Add the pumpkin, oatmeal/water mixture and vanilla, mixing on slow speed until well blended.
While mixer is still going on slow, add the flour, one cup at a time. Next, add the pumpkin spice, baking soda and salt. Blend until well incorporated.
Pour cake batter into prepared Bundt cake. Bake for 60 minutes or until a knife inserted into the center comes out clear.
Allow to cool in pan for 10 minutes then invert onto a large cake plate. If desired, dust with powdered sugar.