Rinse the capers under cold running water, rinse and pat dry with paper towel.
Put 1 tablespoon of olive oil in a medium size skillet over medium heat. When hot add capers and fry for 1 minute, gently shaking the pan. Add the tomatoes and the olives. Season with salt and pepper and cook for 2 – 3 minutes, just enough to warm.v
In a small bowl, whisk together the remaining 2 tablespoons olive oil, the Dijon mustard and vinegar. Add the tomatoes and mix well.
In a large straight skillet heat the remaining olive oil over medium heat. Once the oil is hot, add the fillets and cook 5 to 6 minutes on each side, or until cooked through completely and the fish flakes easily.
Top the fillets with the tomato relish and enjoy.