Put the bananas in a greased baking dish.
Sprinkle with the sugar and rum.
Bake in a moderate oven (180°C/350°F or Gas Mark 4) for 15 minutes.
Remove from the oven and allow to cool for 10 minutes.
Reset the oven to warm (170°C/325°F or Gas Mark 3).
Mix the macaroons with the butter.
Pour the cream over the bananas and sprinkle over the macaroon mixture.
Bake for a further 20 minutes.
Serve hot, in the baking dish.