Shahi means royal. Shahi dishes were introduced in the royal kitchen during mughal period.
Shahi paneer is one of the most popular Indian dishes. It is a classical north indian or punjabi curry, where paneer is cooked in a rich and creamy gravy with onions, spices, yogurt(dahi), and of course paneer in dry fruit sauce. This curry is more creamy and sweet in taste as compare to other traditional paneer based curries, due to the use of dry fruits. It is an ideal gravy based curry is liked by a large number of people, specially Punjabi people and widely available in Indian restaurants. This dish is not everyday thing. There is no one who eat Shahi paneer daily. It was made on some special events like birhday, festivals, or any other occasion of god.
So, it is very special dish and need to be cook properly.
Many people make shahi paneer with tomatoes. But it is not the proper way as it is a dish of mughal period and tomatoes were not available at that time. And the mixture of yogurt(dahi) and tomatoes will make very tangy taste.
If you want to make paneer with tomatoes then try another recipe Paneer Butter Masala.