Roast rack of lamb with courgettes and tomatoes

Fruit and vegetables

3 yellow courgettes, cut into 4mm/¼in slices

3 green courgettes, cut into 4mm/¼in slices

2 garlic cloves, chopped

3 onions, sliced

15g/½oz fresh thyme, leaves picked and stalks reserved

8 plum tomatoes, cut into 4mm/¼in slices