Red Onion Tarte Tatin recipe | Delia Smith

Ingredients

• 2½ lb (1.15 kg) red onions
• 1 oz (25 g) butter
• 1 level teaspoon caster sugar
• 6 small thyme sprigs
• 1 level tablespoon chopped fresh thyme
• 1 level tablespoon balsamic vinegar
• salt and freshly milled black pepper
• 3 oz (75 g) plain white flour
• 2 oz (50 g) plain wholemeal flour
• 2 oz (50 g) soft butter
• 1 oz (25 g) Cheddar cheese, grated
• 1 teaspoon chopped fresh thyme leaves
• a few shavings Parmesan (Parmigiano Reggiano)