Preheat oven to 350F. Grease an 8 inch square pan and line it with overhanging parchment paper
In a medium-sized bowl, whisk together the flour, cinnamon, baking soda and salt.
In a separate large bowl, whisk together the sugar, oil, mashed banana, milk and vanilla.
Add the dry ingredients to the wet mixture and whisk until just combined.
Pour the batter into the prepared pan and gently tap the bottom of the pan off the counter to help release any air bubbles.
Bake for 24-26 minutes, or until a toothpick inserted into the center comes out clean.
Let cool on a wire rack before frosting.
To make the frosting, add the cream cheese, butter and cinnamon to a mixing bowl and use an electric mixer on medium-high speed to cream together. Gradually add the powdered sugar until the frosting is smooth and creamy.
Spread the frosting onto the cooled cake, slice and serve.
Store in an airtight container in the fridge for up to 5 days.
Notes
If you don’t have a kitchen scale to weigh your flour and sugars, be sure to measure them using the spoon and level method with a dry measuring cup.
In my experience, plant-based butters and cream cheeses don't need a lot of time to soften at room temperature compared to their dairy counterparts.
Some dairy-free cream cheeses may not even need to be left at room temperature. If the variety you're using seems soft already, I would skip the step of bringing it to room temperature.
For a thicker and sweeter cream cheese frosting, just add more powdered sugar.
If your powdered sugar is lumpy, sift it before adding it to the mixer. This will ensure you get a smooth frosting.