Step 1

Preheat the oven to 355°F or 320°F convection. Butter a 10 by 4-inch loaf pan and line with parchment paper.

Step 2

Reserve half a banana for the top of the cake and mash the remaining bananas well.

Step 3

In a bowl, whisk together the oil, brown sugar, vanilla, rum, eggs, and buttermilk or yogurt. Add the mashed banana and set aside.

Step 4

In another bowl, whisk together the flour, baking soda, baking powder, and salt. Fold this into the banana mixture until just combined, then pour into your prepared pan. Smooth the top with an icing spatula or rubber spatula and place the reserved banana half, cut lengthwise, on top. Sprinkle with the sugar.

Step 5

Bake for 40 to 50 minutes, until an inserted skewer comes out clean and the top of the cake has set and starts to caramelize. I sometimes use a kitchen blowtorch to help this along. Leave to cool in the pan for about 10 minutes, then transfer to a wire rack to cool completely.