Mash bananas with a fork, set aside.
Sift together low protein flour and baking soda, mix well.
Add in a tray of water (about 2 cups) in the oven, preheat oven to 160°C/320°F.
In a clean mixing bowl, whisk egg whites on low speed until foamy. Add in cream of tartar, whisk until small bubbles are formed. Add in fine sugar gradually, whisk on low speed until stiff peak (the peaks will point straight up and hold). (Reminder: Egg whites and equipment used to beat egg whites must be grease-free and water-free, including egg yolk. It is advisable to clean the egg shells and equipment with dishwasher detergent, then dry with a clean cloth. Use a clean small bowl to separate the egg yolk and egg white, if the egg yolk cracks, don’t use that egg white.)
Combine mashed bananas, salt, sugar and egg yolks, mix well. Add in corn oil, mix until combined. Sift in flour, mix until just combined (do not overmix).
Add meringue into batter in 4 batches, mix gently using balloon whisk.
Fold gently until well mixed with spatula.
Tap mixing bowl on countertop for a few times to burst large bubbles, then pour batter into 22-cm loose base tube pan (do not grease), tap tube pan gently again on countertop for a few times.
Put into preheated oven, bake at 160°C/320°F for 45 minutes, then at 180°C/355°F for another 10-15 minutes, until the top is golden brown. (Reminder: The heat for different oven is different, the suggested time is only for reference, adjust the baking time base on your oven if necessary.)
Turn the pan upside down onto a wire rack (at least 6″ from the countertop), set aside until fully cooled.
Unmould the banana chiffon cake when it has fully cooled down.