It is perfectly alright to cook tomato sauces in cast iron, especially a well-seasoned one which should defend against the acidity attacking the metal fairly well. Another way is to neutralise the acid with some sodium bicarbonate. Oh, and
> You will get tremendous amount of iron oxide (rust) into the food to the point when you can taste it
is generally not a problem. In fact, cereals are fortified directly by adding iron oxide—enough that if a magnet is run over it, it will pick up a substantial quantity of iron filings.
If you're especially concerned about your food tasting iron-y, a good substitute is stainless steel. Bring it up to 200°C, add in a small touch of high smoke point oil, add your proteins, and cook. No sticking.
All my cookware is metal including my spatulas, spoons, pots, and pans etc which are stainless steel, aluminium, or enamelled cast iron. Metal is infinitely more durable and flexible (in terms of where and how it can be used, not literal flexibility à la Young's modulus) than any silicone/plastic/non-stick cookware. You can pop a stainless steel pan directly from the stove into an industrial oven. You can put metal (even cast iron, really) in a dishwasher. You can violently scrub at any metal with steel wool and Cif/Gif to attack stubborn stains. The likelihood of something sticking to it is a small price to pay for the sheer peace of mind and flexibility.
Oh, final point. If scrubbing stuff off is such a pain, get a dishwasher.