Bishul Ak um

Question

"If cleaned in between and Libun done which is heating it until it burns off any food or flavor left behind, then you can cook on it. Now if you can ascertain that all the ingredients used are Ok, like no meat or cheese included, then your only issue would be "Bishul Ak"um" the cooking of a non-Jew. If they let you turn on the fire or put the food on, then you are all set. " If it is not permissable to eat food cooked by a non-jew, then isn't all of the discussion as to whether or not eating in these non-hechshered places moot? Obviously, I am not going to go to the kitchen in any restaurant (or cafeteria) and ask to cook my own food! How does this law apply? How come it does not apply to the dunkin donuts or the subway...does the bread or donut not have to be cooked by a jew as well?