Slice squash into a baking dish (remove seeds if they are large). Add sliced onion, separated into rings. Dot with butter and sprinkle with salt and pepper. Cover and bake in preheated oven for 30 minutes.
Uncover and add cream. Bake for another 10 minutes until brown.
After adding the cream, top with a mixture of grated cheese and breadcrumbs for great flavour and texture.