Season the fish fillet with salt and pepper. Heat the olive oil in a saute pan over medium-high heat. Place the fish in the pan, gently pressing on the flesh. Reduce the heat to medium and cook for 4 minutes on 1 side, turn the fish over, and cook for another 2 minutes, or just until done. Remove from the heat to a serving plate and keep warm.
In a medium saute pan, heat the butter on medium heat. When hot, add the olives, capers, tomato and garlic and cook until warm. Add the dry white wine and fish stock or clam juice. Cook another 2 minutes. Place olive mixture on top of the fish and garnish with basil.