Preheat the oven to 160°C.
Heat 44 ml of oil in a lidded casserole and fry onions until golden-brown.
Add 500 ml water, bring to boil, and simmer until water evaporates.
Fry aubergine and courgette pieces in batches in a separate pan with 59 ml oil.
Add tomato halves to the onions, season, cover, and cook for 8-10 minutes.
Stir all beans, courgettes, and aubergines into the onion and tomato mixture.
Melt butter and remaining oil to coat carrot ribbons and layer them on top.
Cook beetroot slices until soft and arrange them with carrots and thyme.
Bake for 45-60 minutes until the topping is crisp and golden.