OPTIONAL: Preheat oven to 350 degrees. If using pepitas: Line a sheet pan with aluminum foil. Spread the pepitas on the pan in a single layer. Bake for 8 minutes. Remove from oven, transfer to a bowl, and set aside to cool. This step can be done ahead of time!
In a medium bowl, whisk together the flour, baking soda, salt, and spices. Set aside.
In a large bowl, mix the pumpkin puree, eggs, oil, water, sugar, and vanilla. Add the flour/spice mix into the pumpkin mixture and gently combine with a rubber spatula until just combined. Make sure you scrape the sides and the bottom of the bowl for any dry ingredients that may be hiding!Make sure you scrape the sides and the bottom of the bowl for any dry ingredients that may be hiding!
Preheat oven to 350 degrees. Prepare 1 large loaf pan with cooking spray and pour the batter into the pan. I like to place the loaf pan onto a foil-lined baking sheet to catch any spillover and make it easier to move in/out of the oven. Sprinkle the roasted pepitas on top and bake for approximately 50 minutes (2 smaller loaves) or approximately 90 minutes (1 large loaf). You can check the doneness with a toothpick (no crumbs = baked through), or use a thermometer and remove from oven when the internal temperature has reached 190 - 200 degrees. If your loaf is golden brown on top but isn't cooked through, you can gently place a some aluminum foil over the loaf (try not to touch it) to prevent over-browning.
Let cool in pan, slice, serve and enjoy!