Season the fish fillets with salt and pepper. Heat one very large or two medium sized saute pans over medium high heat for a minute, then add the butter. When the butter is sizzling, add the fillets flesh side down and turn the heat to very high. Sear the fillets until golden brown and flip to sear the other side. Remove fillets from pan and reserve on a rack over a plate to catch juices.
Return the pan (or pans) to the heat, add the onions and cook, stirring often, over high heat for 2 to 3 minutes. Add the garlic, jalapeno slices, lime wedges, tomatoes, oregano and olives and saute briskly for 1 minute more. Add the white wine and reduce to half. Add the fish stock and bring to a boil, reduce to a simmer and return fish fillets, along with their juices, to the pan. Finish cooking, covered, about 1 to 3 minutes depending upon the thickness of fillets.
Taste broth and adjust seasoning, then serve immediately in soup plates with a generous puddle of broth and garnish of vegetables on top.
c.1997, M.S. Milliken & S. Feniger, all rights reserved