Sauté the Base: In a large pot, heat 1 tbsp of olive oil over medium heat. Add the 1 medium onion, finely chopped and 3 minced garlic cloves. Sauté until the onion becomes translucent, which should take about 3-4 minutes. Stir in the 1 diced red bell pepper, 1 tsp ground turmeric, 1 tsp paprika, and ½ tsp red chili flakes (if using). Cook for an additional 2 minutes, allowing the spices to bloom.
Build the Broth: Pour in 1 can (400ml) coconut milk and 2 cups fish stock, stirring thoroughly to combine. Bring the mixture to a gentle simmer, allowing the flavors to meld for about 3-5 minutes.
Cook the Fish: Add the 1 lb white fish fillets (cut into chunks) into the simmering broth. Allow the fish to cook for 5-7 minutes, or until tender and easily flaking apart. This is crucial; avoid overcooking to maintain its delicate texture.
Add Lime and Season: Once the fish is cooked, stir in the juice of 1 medium lime and half of the ½ cup fresh cilantro. Season with salt and pepper to taste, ensuring the flavors are balanced and vibrant.
Garnish and Serve: Ladle the soup into bowls, garnishing with the remaining cilantro. Serve hot, accompanied by lime wedges for an extra zesty touch.