this option used to be possible on their website which was a great thing because everyone wants to see the prices in bitcoin as majority of those who enter altcoin market are entering with their bitcoins and would like to see how much they have lost or possibly earned on what they have invested.
you simply had to add a "#BTC" at the end of the link to get it by default, my bookmark is even set to that but they changed it back in 2017 as a manipulation of the market to prevent people from seeing the real dumps.