All you need is 3 ripe bananas, 75ml oil, 50g sugar, 225g flour (plain or Self raising) and 1 tsp baking powder. My own personal hack also needs juice and zest of half a lime, and 1 tsp each of cinnamon and ginger. If you have fresh ginger use that.
Grease or line your tin, and preheat your oven to 180C. Peel your bananas, slice and mash with a fork in a large mixing bowl. If the bananas aren't the old and squishy sort, add a little of the oil to start then off. Add the rest of the oil and sugar to the bowl and mix well. It's not pretty right now but trust me, it gets better. Tip in the remaining ingredients and mix well to form a lumpy batter.
Pour the mix into your tin, dust with flour and bake for an hour. If a knife inserted into the centre comes out clean, you're good to go. If not give it another 10 mins and try again. Allow to cool in the tin for 10 mins before removing to settle and firm up.