1. In a skillet over medium heat, heat olive oil. Add onion, garlic, and tomato and cook for 5 minutes. Add tomato purée, olives, and capers and cook over medium heat for 2 minutes.
2. Bring to a boil and add fish fillets, thyme, salt, and pepper. Cover and cook over medium heat for 10 minutes. Set aside.
3. Serve Veracruz-style fish fillet with rice on the side and garnish with chiles güeros and parsley leaves.