Ingredients

• 4 (4 ounce) tilapia fillets
• 2 tablespoons olive oil, divided, or as needed
• ½ teaspoon Cajun seasoning, or to taste
• 1 pinch salt and ground black pepper to taste
• 2 medium onions, thinly sliced
• 1 (14.5 ounce) can diced tomatoes, drained
• 2 tablespoons capers
• 4 submarine sandwich rolls, split