1. In a large deep frying pan, heat the oil over moderate heat. Add the onion, bell peppers, and salt and cook, stirring occasionally, until the onion is soft, about 5 minutes. Stir in the garlic and sherry; simmer for 1 minute. Add the clam juice and bring to a simmer. Reduce the heat and simmer, covered, for 10 minutes.
2. Transfer the contents of the frying pan to a blender or food processor and puree. Add the almonds and the black pepper. Pulse until the nuts are chopped very fine. Return the sauce to the pan.
3. Bring the sauce just to a simmer and add the fish to the pan. Simmer, covered, until just done, 10 to 12 minutes. Slice the fish on the diagonal and serve with the parsley sprinkled over the top.
Fish Alternatives: Though monkfish is quite firm, a relatively firm, thick white fish, such as haddock, cod, or halibut, would also be delicious braised in this flavorful sauce.
Wine Recommendation: A fresh, fruity but not-too-sweet rosé will complement the Mediterranean flavors here. Look for a rosé from Rioja to carry out the Spanish theme, or try one from southern France.