hello, welcome to just answer. my name is XXXXX XXXXX and i will be happy to assist you with your problem. you need to remove those burners first. the burners turn about a 1/4 turn to the left. they can be tight. they will then lift off. under them is a Philips screw. remove the wires and the 4 screws. then the top will lift off
I believe they are stuck there may be spilled food under them. What can I use to loosen them with, ie WD40 or oven cleaner?
you could try some wd-40 but it is almost impossible to get it into where these get gulled. they madea tool to remove these but i dont know if it is still available. i have laid a towel over them a tapped them with a hammer lightly to free them. you must be careful to not chip the porcelain.