Preheat oven to 350 degrees F. Line the bottom of a 9x13" cake pan with parchment paper, and grease the sides.
In a small pan over medium-low heat, combine the coconut milk, coconut oil and brown sugar. Whisk until smooth and blended, about 2 minutes. Do not overcook. Pour the caramel into the pan, spreading out evenly over the parchment. Place the sliced bananas cut side down, arranging how ever you like but try to ensure there's minimum space between each slice as there will be even bigger gaps once baked. If the bananas are all the same length, placing them so they are spoon each other is the easiest way to arrange them.
In the bowl of a stand mixer (or with a fork/whisk in a medium sized bowl), combine the mashed bananas, plant milk, oil, vinegar and vanilla, whisking until well blended.
In a medium sized bowl, sift the flour, sugar, baking powder, baking soda, salt and cinnamon. Add this to the wet ingredients and mix only until the flour is just wet. Do not over-mix.
Drop the batter gently over the caramel and sliced bananas and smooth out the top with a spoon or spatula.
Bake in the oven for 30-35 minutes or until golden brown and a toothpick inserted comes out with clean or with a few cooked crumbs. Let the cake cool for about 20 minutes before inverting onto a serving tray. Enjoy!