• Preheat the oven to 180°C.
• In a saucepan, melt the butter and sugar over low heat; remove from the cooker and add the egg.
• Add the ripe banana, slightly crushed, and vanilla.
• Add the dry ingredients without over-mixing.
• Butter and flour a cake tin.
• Bake for 45 minutes, checking the baking status with a knife.