T.N.
You can use a cleanser like Bar Keeper's Friend, or I also use foaming Easy Off, which is an oven cleaner and also works well on stove tops. You spray it on and let it soak for half an hour, then wipe/scrub it off. My mom would put tin foil down below the burners to catch any food that boiled over or spilled, and it's really easy to throw that away and replace it with clean foil instead of having to scrub down there.