Squeeze the lemon juice over the fish fillets and season with salt. Set aside.
Heat a few tablespoons of olive oil in a saucepan over medium-high heat. Add the onion rings, carrot matchsticks, and green bell pepper strips. Sauté for 5-8 minutes until just tender. Add the white wine vinegar, chili powder, black pepper, white pepper, and crushed bay leaves. Remove from heat.
Heat olive oil in a pan over medium-high heat. Fry the fish fillets until golden brown and crispy. Transfer to a flat, wide dish and pour the hot vegetable mixture over the fish.
Serve hot with boiled potatoes immediately, or cool to room temperature, refrigerate covered for up to 1 day, then reheat gently over medium heat before serving.