Line a 20 x 20cm baking tin with baking parchment. If you're using a loose-bottomed tin then fold the parchment at the corners so it goes up the sides of the tin too. Otherwise the caramel will leak out into the oven.
Put the sugar, butter and golden syrup for the topping in a small saucepan. Cook until all the sugar and butter have melted. Stir gently and pour into the tin. If necessary tilt the tin backwards and forwards so the layer of caramel covers the bottom of the tin.
Slice the bananas into pieces about 2cm thick. Place them in the caramel.
Start to make the cake. Mash the bananas with a fork then mix into the yogurt. Set aside.
Put the butter and sugar in a large mixing bowl. Whisk till pale and fluffy.
Add the vanilla extract and eggs, one at a time, whisking after each one.
Sift the flour and spices and gradually fold into the mixing bowl. Then fold in the banana and yoghurt mixture too.
Spoon the batter into the cake tin on top of the caramel and bananas.
Bake at 180C for about 45 minutes. Test with a skewer to see if it's cooked. If necessary bake for a little longer.
When ready, let the cake stand for a couple of minutes out of the oven. Place a plate on top of the tin and turn it over to remove the cake.
Serve warm with cream, custard or ice cream.
Nutritional information is approximate and a guideline only.