Rinse the fillets and shake off excess water, place in a large zip lock bag. In a mixing bowl, mix together the Marinade ingredients and pour into the zip lock bag. Squeeze out all the air as possible, squish the fish around to coat them and place in the fridge for 90 minutes to marinate.
Prep the vegetables. Slice the onion in half from top to bottom, then thinly slice each half. Slice the bell peppers into thin strips. And finally, shred the carrot.
Heat a splash of olive oil in a large non stick pan on medium heat. When hot, add the onion and cook until they are soft, about 2-3 minutes, then add the carrot and bell peppers, stir together and cook until the carrots and peppers are softened yet the peppers still crunchy, about 4 minutes or so. Remove the vegetables to a plate and set aside, and set the pan aside as well.
Preheat your oven to 190 C (375 F) and get out a large baking dish, like a 7x11 or 9x13 dish.
After the fillets are done marinating, remove the fillets to a strainer to drain and discard the marinade. Now take that same pan you used, heat another splash of olive oil on medium high heat.. When the oil is hot, fry the fillets, work in batches if needed. Just fry to lightly brown both sides, about 2 minutes per side. You are not trying to cook them through, just lightly browned.
Now take half of the vegetable and spread in an even layer on the bottom of the baking dish.
Place the fillets on the vegetables, slightly overlap them if needed to get all the fillets in the dish.
Mix together the ketchup and mayo in a small bowl, and brush this evenly onto the fillets.
Spread the remaining vegetables evenly over the fillets. Sprinkle with salt and pepper, to taste.
Cover the dish with foil, now we are going to steam the fish for the final cooking. Bake for 15 minutes.
Serve with mashed potatoes and butter or buttered egg noddles for a perfect meal.
