Make the marinade: combine all ingredients up to and including oregano. Season the fillets with salt, pepper, and parika. Nestle the fillets into the maride and make sure they're covered. Top with sliced onions and cover and refrigerate for at least one hour.
Make the cod: Par boil sliced potatoes by placing them in a medium pot filled with cold, salted water. Bring to a boil over high heat, then reduce heat to medium and simmer for approximately 5-8 minutes, until they are half-cooked. Drain and set aside.
Heat the oven to 375 degrees. Prepare a baking pan or sheet by lightly greasing with olive oil. Arrange potato slices on the sheet in one layer. Take the sliced onions from the marinade and layer on top of the potatoes. Add red pepper slices.
Arrange the fish fillets on top of the vegetables. Pour the white wine and sherry vinegar over the fish. Drizzle with some Spanish olive oil and place in middle rack of oven. Cook until fish is opaque and vegetables are tender, about 25-30 minutes.
Make the topping: Combine ingredients in a small bowl, mix well.
Top fish with diced olive topping and serve with coconut rice.