Preheat oven to 350 degrees. Grease an 8-inch round cake pan, then line the bottom with parchment paper.
Roughly mash the (2) bananas in a large bowl, then beat in the eggs. Stir in the oil and coconut milk. Stir in the 1 1/2 cups of brown sugar into the banana mixture until well combine. Fold in the flour and the extracts.
Add the cake mixture to the prepared pan. Bake for 1 hour until done. Let cool in the pan for 10 minutes; turn out onto a wire rack to cool completely.
To make the frosting, beat together the mascarpone cheese with powdered sugar, adding in lemon juice and extracts until smooth and creamy. Spread over the cooled cake.
Puree the coconut in a food processor or chop with a knife to make it very fine.
To make the salted caramel topping, in medium sauce pan add water and sugar. Bring to a boil, stirring constantly, about 4 minutes. Reduce heat after it begins to boil to a simmer, making sure to stir, until sugar becomes golden, about 6 minutes. Immediately add cream to sauce and mix in.
Stir constantly as "caramel" begins to foam. Bring sauce to 225 degrees and then remove from heat. Add coconut and vanilla.
Allow to cool to about room temperature before spreading on top of the cake, leaving 1/2 inch around the outside. (It will run down the sides.)
Garnish the top of the cake with a sliced banana; serve.
(If the cake is going to be made up ahead of time, soak the sliced banana in lemon juice for a few minutes and drain, before garnishing the cake.)