A good way of getting burn marks off of a countertop is to first put some Dawn Dish Soap onto the burn mark and then use a sponge with some water to scrub the burn mark and sometimes it will come off with the dish soap and hot water.
If not you can then mix some baking soda and water together to make a paste and put it on the burn marks and then use a scrub brush to gently scrub the countertop where the burn mark is.
It should remove the burn mark if the burn mark is not too severe.
You can also mix some vinegar and baking soda together and the vinegar will work along with the baking soda to remove the tougher burn marks.
Or apply some rubbing alcohol to the burn mark along with the baking soda and then use a scrub brush to scrub the countertop.
The Dawn Dish Soap and baking soda usually works for me to remove burn marks if I remove the burn marks soon after they happen.
But the longer you leave the burn marks on the countertop the harder it will be to remove the burn marks from the countertop.