In a large bowl, stir pumpkin, 1 cup granulated sugar, brown sugar, 3 egg whites, buttermilk and oil, until combined.
In a separate bowl, whisk together flour, baking powder, baking soda, spices and salt. Add to pumpkin mixture and fold gently just until moistened.
In a small bowl, beat cream cheese, remaining granulated sugar and remaining egg white until well blended.
Spoon half the pumpkin batter into a 9x5-inch loaf pan sprayed with cooking spray. Spread the cream cheese mixture in a layer over that batter. Top cream cheese layer with remaining pumpkin batter (You will want to spread the top pumpkin layer a little bit with a silicone spatula, but it is ok if a little cream cheese is still visible).
Sprinkle the top layer with chopped pepitas, if desired. It helps to gently pat the pepitas into the batter
Bake for 1 hour to 1 hour 5 minutes, or until a toothpick inserted in the center comes out clean. Loosen bread from sides of pan; cool in pan for 10 minutes. Remove from pan to wire rack; cool completely.
Recipe by Alida's Kitchen at https://www.alidaskitchen.com/2011/11/15/layered-pumpkin-loaf/