They do, and it's currently voted Dublin’s second best Afternoon Tea by OnSpecial, second only to the Merrion Hotel. We saw two parties having afternoon tea when we were there, and it looked beautifully presented.
On the Bon Appetit website however they explain you have to book ahead:
"Afternoon Tea is served Friday to Sunday from 12:30 to 15:00 by advance reservation only; 24 hours notice required."
Get quick answers from Bon Appetit staff and past visitors.