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.
I really disagree on the tomato sauce being okay in cast iron. Cooking high acidity food will absolutely strip all the seasoning off your pan if done for long enough. It has nothing to do with rust.
> Cooking high acidity food will absolutely strip all the seasoning off your pan if done for long enough
That statement doesn't seem compatible with the chemistry. The seasoning on a cast-iron is a (plastic) polymer that is fairly resistant to acid attack—especially the weak acids in food. It's why the strongest and most concentrated acids are stored in plastic and not glass beakers.
Try it. 60 minutes boiling tomatoes takes the seasoning right off. its recommended as a way to restart seasoning from nothing. vinegar is also an alternative.
You generally wouldn't fry burgers in the same cast iron container in which you make sauce, because of their different shape that determines their purpose. Only cast iron used for frying needs the varnish.
> 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.