Sift the flour and salt into a bowl and coat the butter cubes in flour.
Mix 125ml of water with lemon juice and stir into the flour to form a dough.
Roll the dough into a 35cm x 20cm rectangle and perform several envelope folds.
Repeat the rolling and folding process 5 times before chilling the pastry overnight.
Preheat the oven to 180°C.
Boil the sugar with 15ml of water in a pan until it reaches a light golden syrup.
Swirl in the salted butter until melted and let the caramel cool slightly.
Arrange banana slices over the caramel in the pan.
Cover the bananas with a pastry circle, tuck in the edges, and pierce with a fork.
Bake for 45 minutes until golden and immediately invert onto a plate to serve.