Cuban Style Bass

2 tablespoons extra virgin olive oil
1 1/2 cups thinly sliced white onions
2 tablespoons minced garlic
4 cups seeded, chopped plum tomatoes
1 1/2 cups dry white wine
2/3 cup sliced stuffed green olives
1/4 cup drained capers
1/8 teaspoon red pepper flakes
6 (6 ounce) fillets bass
2 tablespoons butter
1/4 cup chopped fresh cilantro

Heat oil in a large skillet over medium heat. Sauté onions until soft. Stir in garlic, and sauté about 1 minute. Add tomatoes, and cook until they begin to soften. Stir in wine, olives, capers, and red pepper flakes. Heat to a simmer. Place bass into sauce. Cover, and gently simmer for 10 to 12 minutes, or until fish flakes easily with a fork. Transfer fish to a serving plate, and keep warm. Increase the heat, and add butter to sauce. Simmer until the sauce thickens. Stir in cilantro. Serve sauce over fish.