Tilapia with Olive Mushroom and Tomato Sauce

Bahan-bahan (4 porsi)

• 1 tablespoon olive oil
• 1 small onion, (cut into thin wedges)
• 1 medium garlic clove, (minced)
• One 14.5-ounce can diced tomatoes, (undrained)
• 1 cup sliced cremini or button mushrooms
• 16 large pimiento-stuffed olives, (coarsely chopped)
• 1 tablespoon snipped fresh oregano ((or ½ teaspoon dried, crushed))
• ¼ teaspoon salt
• ⅛ teaspoon freshly ground black pepper
• Four 6-ounce tilapia fillets