In a bowl mix soy sauce, tomato, sweet red pepper, thyme, salt and black pepper.
Place fillet into the marinade and squeeze it well so that the marinade gets deeper. Leave for at least 30 minutes. (Can leave it for up to 20 hours in the fridge. The longer it is marinated the better).
Heat oil in a skillet over medium-high heat. Cook fillets from all sides until golden.
Preheat oven to 190C. Cover fillets with foil all around but not tight.Place fillets on a baking sheet and bake for 20 minutes.
Let rest for 5 minutes before serving.
Optional: Tomato and sweet pepper can be substituted with 1 tbsp tabasco sauce.