Preheat your oven to 175°C (350°F). Lightly grease the base and sides of a square 8" pan with some oil or vegan butter, then line with parchment paper.
In your food processor, combine the gluten-free flour, almond flour, vegan butter, maple syrup, and salt until the ingredients stick together to form a dough.
Evenly press the dough into the base of the pan and smooth it out with a spatula or flat bottomed glass. With a fork, gently prick the dough several times. Bake for 15-18 minutes until slightly browned, then allow to cool to room temperature.
Slice the bananas into coins and add them to a bowl with the lemon/lime juice. Coat both sides of the banana slices in the juice and then transfer them to a plate lined with kitchen paper or a clean tea towel. Gently blot the excess moisture from them and arrange them on top of the shortbread base in an even layer.
To make the caramel, add the peanut butter, maple syrup, coconut oil, coconut milk, vanilla extract, and salt to your food processor and blend until smooth. Using a spatula, spread the caramel over the sliced bananas in an even layer. Place in the fridge to set for at least 2 hours (overnight if preferred).
Melt the chocolate over a double boiler and use a spatula to spread it over the caramel in an even layer. Place in the fridge for 15 minutes to set.
To slice, place a sharp knife in a jug of boiling water to heat it. Wipe the knife dry and gently cut, allowing the heat from the knife to melt through the slices.