Preheat your oven at 180°C. Grease a 9 x 9 x 2 inches (23 x 23 x 5 cm) square baking dish/pan or 11 x 7 x 2 inches (28 x 18 x 5 cm) rectangular baking dish/pan or 10 x 2 inches (25 x 5 cm) round baking dish/pan.
On a small sauce pan, heat the brown sugar/jaggery till it melts then add in the butter/margarine. Stir and allow it to melt as well then finally add in the lemon juice/apple cider vinegar. Then spread the mixture evenly over the bottom of your baking dish/tin. Arrange the banana slices on top.
In a large bowl, add the flour, baking powder, sea salt and sugar. Whisk together till well combined then set aside.
On a flat plate, mash the peeled bananas.
In another bowl, whisk the eggs then add in melted unsalted butter, vanilla extract and the mashed ripe bananas. Mix till well incorporated.
Bring together the dry and wet ingredients and mix till all is incorporated.
Pour the batter into the prepared baking dish/tin, spreading it evenly over the banana slices.
Bake for about 30-35 minutes at 180°Cor until a toothpick or cake tester inserted in the center comes out clean.
Place the baking dish/tin upright on a wire rack and allow to cool for about 10-15 minutes then invert onto a serving platter.
Slice & enjoy warm or cold.