1. Preheat the oven to 350°F/175°C
2. Spray a 9×9 pan with nonstick spray and set aside.
3. In a small pot bring the water to a boil. Add in the oats, stir and remove the pot from the heat. Allow the oats to soak for 20 minutes.
4. In the bowl of your stand mixer fitted with the paddle attachment mix the butter and sugar together on medium speed for 2 minutes until light and fluffy. Add in the vanilla and the eggs and mix until combined, scraping the sides of the bowl as necessary. With the mixer still on medium speed add in the salt, baking soda and cinnamon and mix until incorporated.
5. Turn the mixer to low and add in the oats and the flour, mixing until just combined.
6. Spread the cake batter into the prepared pan and bake for 35-40 minutes or until the cake is set in the center and a toothpick comes out clean.
7. Allow the cake to cool completely in the pan.

Frosting

1. In the bowl of your stand mixer fitted with the paddle attachment mix the butter and cream cheese together on medium speed until smooth, 2 minutes. Turn the mixer to low and add in the powdered sugar and milk. Mix for another minute until the frosting is creamy.
2. Spread the frosting on top of the cooled cake.
3. Serve immediately or store airtight for up to 3 days.