Sieve together flour, cinnamon, salt and baking soda. Set this aside.
Grease a 8 by 4 inch loaf pan with butter.
Beat the egg and set aside.
Preheat the oven to 160 C for atleast 15 mins.
Mash the bananas very well either with a masher or puree them.
Add sugar and vanilla. Mix well until sugar dissolves.
Add butter and beaten egg.
Mix together flour in 2 parts with the wet ingredients just until combined. Avoid over mixing and make sure there are no lumps.
Making banana bread
Transfer the batter to the greased pan.
Bake for 60 minutes or until a skewer inserted comes out clean. You may need to adjust the baking time by 5 to 10 mins depending on your oven. But keep an eye after 55 mins. Mine was done exactly after 60 mins.