Start by greasing a rectangular 9x13 pan and preheating the oven to 350°Fahrenheit (175 °C). In a medium bowl place the flour (2 cups), baking soda (2 tsp), sea salt (½ tsp), cinnamon (2 tsp), and nutmeg (1 tsp). Use a whisk to mix thoroughly.
In another bowl, place the oil (¾ cup), brown sugar (1 cup), pumpkin puree (2 cups), vanilla (2 tsp), and eggs (3). Use the whisk to combine well. Dump the flour mixture into the wet pumpkin mixture, using a scraper fold the mixture together just until mixed, don’t overmix.
Pour the batter into the prepared pan, spread the batter until it is evenly distributed in the pan. Bake for 25-30 minutes at 350°F (27 minutes comes out perfect for me every time), it will be ready when the middle of the cake slightly springs back when you touch it. Let it cool.
Optional Icing: Place the softened cream cheese, maple syrup (4 tbsp) and cinnamon if using, into a mixer with a whisk attachment. Whisk for 2 minutes, then scrape down the sides of the bowl before whisking another 3-5 minutes until completely smooth. Spread icing on the cooled cake.
Storing: Cover, and store cake in fridge if using icing. Cover and keep at room temperature if you make the cake without icing. It will stay good for 1 week.