What defines a “natural-born citizen” are the U.S. citizenship laws in effect at the time of your birth.
At the time of Ted Cruz’s birth he met the legal requirements then in effect for automatic U.S. citizenship and therefore did not have to apply for naturalized citizenship.
This is incorrect. The meaning of "natural born citizen" cannot be redefined by congress. They can't make it mean something new.
It's meaning is set in stone, and it means the exact same thing as it did in 1787 when it was made a requirement.
And let me be clear, "natural born citizen" predates the US Constitution because that condition was created by the Declaration of Independence. Anyone born prior to the Declaration of Independence was a British Subject. Those born after, (to an American father) was a "natural born citizen."