Preheat the oven to 350°F / 175°C. Butter a 7" springform pan and line it with parchment paper on the bottom and sides.
In a medium-sized mixing bowl, mash the banana until it's completely smooth. Then, add in the sugar, oil, egg, vanilla, and crushed pineapple (with the juice!) Whisk until well combined.
Add in the flour, baking powder, baking soda, salt, cinnamon, and pecan flour. Gently mix the dry ingredients into the wet ingredients until only a few streaks of flour remain. Then, add in the chopped pecans and mix just until the last streak of flour dissapears.
Pour the cake batter into your prepared pan. Bake for 40-45 minutes, until a toothpick inserted in the center of the cake comes out with only a few moist crumbs.
Brown Sugar Caramel Sauce
In the meantime, make the brown sugar caramel sauce. Add the sugar to a small saucepan set over medium heat. Stir occasionally until the sugar begins to melt, then stir constantly until the sugar has completely melted.
Add in the butter and whisk until the mixture is smooth.
Remove the caramel from the heat and slowly whisk in the heavy cream until it's completely incorporated into the caramel. Then, whisk in the salt.
Transfer the caramel to a heat-safe container and set it in the fridge until you're ready to assemble the cake.
Cream Cheese Frosting
(Save this step for when the cake has cooled and you're ready to assemble it.) In a large mixing bowl, with a hand or stand mixer, beat together the cream cheese, butter, and salt until the mixture is light and fluffy.
Add in half of the powdered sugar and beat until combined. Then, beat in the rest of the powdered sugar along with the vanilla. Continue beating the mixture for an additional 2 minutes.
Assembly
Once the cake has fully cooled to room temperature, cut it in half horizontally.
Set the bottom half of the cake back into the springform pan and evenly spread ½ of the cream cheese frosting over it. Then, top the cream cheese with ~⅔ of the brown sugar caramel sauce.
Place the top half of the cake on top, then remove the cake from the springform pan. Top the cake with the remaining cream cheese frosting (I used a large round tip to pipe the frosting on top) and with the remaining brown sugar caramel sauce. I also topped mine with a couple pineapple flowers. Slice, serve, and enjoy!
*Make homemade pecan flour by blending pecans in a food processor until they resemble fine crumbs. Be sure to not over-mix or you'll end up with pecan butter!