Step 1

Heat oven to 350 degrees F (177 degrees C).

Step 2

In a bowl, whisk together the flour, baking soda, cinnamon and salt together. Set aside.

Step 3

Mash the banana with a fork in a separate small bowl. Add the sugar and whip the banana and sugar together.

Step 4

Add the melted butter, the egg yolk, and the vanilla; mix well.

Step 5

Mix in the dry ingredients just until incorporated.

Step 6

Pour the batter into a lightly buttered 8-ounce ramekin or other baking dish of similar size.

Step 7

Bake for 30 minutes, until golden brown.

Step 8

Remove from the oven and cool slightly before eating.