Take a baking tin lined with greased butter paper or parchment paper.
Take one banana and cut it from the centre lengthwise into two parts.
Place both the banana strips at the bottom of baking tin with flat sides downwards. Keep aside.
Take a blender and add rest of the 5 bananas with jaggery in it.
Blend them to a fine puree.
Transfer puree in a bowl.
Add semolina, salt, vanilla essence and walnuts. Mix. If the batter appears to be much thick, mash one more banana and add to the batter.
At last, add ENO & whisk together into a fine batter. The batter will turn frothy. Immediately transfer the batter into baking tin over the laid down banana strips.
Level the batter with spatula and tap the tin twice to release air bubbles.
Bake in preheated oven for 30 to 35 minutes @180°C in middle rack with both the rods on.
Pass the cake through toothpick test by inserting a toothpick in cake. If toothpick comes out clean it's a sign that cake is perfectly baked.
Let cake turn cool on cooling rack.
Invert and enjoy.