1. Prepare the Topping:
In a 20 cm (8-inch) non-stick skillet, melt the unsalted butter over low heat.
Add the raw sugar and stir for about 5 minutes until it starts to dissolve and form a light caramel.
Slice the bananas into rounds and arrange them in a single layer over the caramel. Cook for a few minutes until they soften and caramelize slightly.
2. Make the Cake Batter:
In a mixing bowl, whisk together the egg and sugar until light and frothy.
Add the milk, salt, and vanilla extract, and mix until well combined.
Sift together the flour and baking powder, and gently fold them into the wet ingredients until just combined.
Stir in the vegetable oil until the batter is smooth.
3. Assemble and Cook the Cake:
Carefully pour the cake batter over the caramelized bananas in the skillet, spreading it evenly.
Cover the skillet with a lid and cook over very low heat for about 25 minutes, allowing the cake to cook through without burning the bottom.
Check the cake by inserting a toothpick into the center. If it comes out clean, the cake is done; if not, cook for an additional 5 minutes.
4. Cool and Serve: