16 garlic cloves, divided
½ cup plus ¼ cup olive oil
6 (8-ounce) Halibut or cod fillets
1 large white onion, halved, thinly sliced
1 large red bell pepper, thinly sliced
1 large green bell pepper, thinly sliced
1 large yellow bell pepper, thinly sliced
1 cup chopped fresh cilantro
1 cup sliced large green olives (about 24)
4 bay leaves
2 teaspoons dried oregano
½ cup dry white wine
1 ½ cups crushed tomatoes
1 ½ tablespoons drained capers from jar (omit if you cannot find them kosher for Passover and/or add a few extra olives)
Puree 10 garlic cloves in mini processor; transfer to 11x7x2-inch glass baking dish. Add ½ cup oil, 1 ½ teaspoons salt, and 1 ½ teaspoons pepper to garlic; whisk marinade to blend. Add fish to marinade, cover and chill 2 hours, turning fish occasionally.
Chop 6 garlic cloves. Heat ¼ cup oil in skillet over medium-high heat. Add chopped garlic, onion, peppers, cilantro, olives, bay leaves, and oregano. Cook until vegetables are soft, stirring often, about 15 minutes. Add wine, stir 1 minute. Add tomatoes and capers; simmer 2 minutes. Season sauce with salt and pepper.
Heat large nonstick skillet over medium-high heat. Add fish to skillet with marinade still clinging. Cook until golden and just opaque in center, about 5 minutes per side.
Discard bay leaves from sauce. Divide sauce among plates. Top with fish.