Natalie's Trinidadian fish stew

INGREDIENTS

• 2 limes , juice and grated zest of 1, the other halved for serving
• 1 skinned white fish fillets, such as cod or hoki, about 175-200g/6-8oz each
• 2 lemons , juice only
• 2 x 15g packets fresh thyme (you need a lot for the aroma)
• ¼ tsp white peppers
• 1 tbsp dark rum
• 3 tbsp vegetable oil
• 1 onion , cut into thin rings
• a handful of fresh coriander , chopped
• 2 garlic cloves , chopped
• 1 beefsteak or 3 normal tomatoes , sliced
• 2 tsp dark muscovado sugar
• shake of Angostura bitters , optional
• basmati rice or boiled potatoes and steamed vegetables, to serve