Is it possible to permanently cure someone with a learning disorder?

No. By learning disorder you mean a learning disability, then no, it's not curable. Ld is a neurological condition that impedes (some or all of) a person's ability to read, write, speak, spell, do math, & reason. It also affects a person’s attention, memory, coordination, social skills & emotional maturity. These can be treated but not cured.
Wiring issue. Think of any LD as a wiring issue. The affected persons brain fails to process the information the way others do because their brain is wired up differently.You help this by finding their areas of strength and work to present materials in a way they can grasp them better.No pill/diet or other therapy will change the wiring.You work with what they have and teach them how to use their strengths in.