Zucchini with Cheese (Kousa bi Gebna)

This is one of those never-fail, easy to prepare dishes that is always appreciated - particularly by guests who usually suspect it must be more complicated to prepare than it is.

There are only five main ingredients: onion, zucchini (courgettes/summer squash), eggs, butter and cheese.

For me it's a lunch dish, but it would be perfectly OK as a light evening meal too. This recipe is the main reason I bought the new edition of Claudia Roden's book when the old one eventually fell apart.

Edited to add that I know this looks a bit like the (usually) firmer-setting frittata/Spanish omelette/quiche, etc., sort of dish, but is much less dense and presents as if a little wine sauce might be involved.

Incidentally, I often use a mixture of gruyere and parmesan cheese, although cheddar will do at a pinch.