cause

usually describes how something happened.

reason

usually describes why something happened.

Revenge was the main reason for the fire. (why)
Spilled gasoline was the cause of the fire. (how)

"Cause" can use either "for" and "of" depending on circumstances.
"Reason" uses "for" in order to explain something.

cause

usually describes how something happened.

reason

usually describes why something happened.

Revenge was the main reason for the fire. (why)
Spilled gasoline was the cause of the fire. (how)

"Cause" can use either "for" and "of" depending on circumstances.

cause for complaint
cause of the complaint

"Reason" uses "for" in order to explain something.

reason for complaining
reason to complain