I can highly recommend the restaurant PLACHUTTA WOLLZEILE for a special meal. It’s in the centre of Vienna.
They are famous for their Tafelspitz, which is what you should have if you go there.
It’s a Viennese boiled beef dish. It was superb. Very flavoursome and delicious. It’s an historical dish, check out the blurb here. https://www.plachutta-wollzeile.at/en/tafelspitz
The restaurant is very nice (so slacks and a shirt ) and perfect for a pre-dinner drink.