½ onion, cut into four wedges
½ onion, peeled and thinly sliced
½ large orange
1½ large oranges, freshly squeezed juice only (around 150ml/5fl oz)
3 tbsp orange marmalade
freshly ground black pepper
2 tsp cornflour (if you want a thinner sauce only use 1 tsp)
2 tsp flaked sea salt, plus extra to season
4 tbsp orange liqueur, such as Cointreau
1.8kg/4lb whole ready-to-roast duck
75ml/2½fl oz red wine