Preheat the oven to 175°C.
Grease a 8-inch baking dish.
Whisk together the flour, baking soda, baking powder and salt in a medium bowl.
In a large mixing bowl, mix the melted butter and sugar until blended.
Add the eggs, mashed bananas, lemon juice, and vanilla extract, then mix well.
Stir in the flour mixture until just incorporated.
Do not over mix.
Transfer batter into the prepared pan and bake 35 minutes, until golden brown and skewer inserted comes out clean.
Spread about 1/3 cup (80ml) of the sauce over top of the baked banana cake.
Return the cake back into the oven, bake for another 5-6 minutes to get the sauce bubbly.
Cool the cake in the pan on a rack for at least 30 minutes.