Preheat the oven to 180℃.
Grease a loaf tin and line with baking paper, leaving two opposite edges overhanging. This will make it easier to lift the cooked banana bread out of the tin.
In a mixing bowl, combine the 300 g self-raising flour and ½ tsp ground cinnamon. Set aside.
In another mixing bowl, whisk the 140 g brown sugar and 75 ml vegetable oil until smooth.
Add the 2 eggs to the wet ingredients, whisk until smooth.
Add the 100 ml milk to the wet ingredients, whisk until smooth.
Add the 200 g mashed banana to the wet ingredients, whisk briefly to combine.
Pour the wet ingredients into the dry ingredients and stir with a spatula or spoon until there's no dry flour remaining.
Pour into the lined loaf tin and smooth the top.
Bake at 180℃ for 45 minutes or until a wooden skewer comes out clean.
Leave to cool in the tin for 10 minutes, this will help the banana bread come out cleanly in one piece. Remove, slice and serve warm with butter.