Cruz was naturalized prior to birth back in 1934. Congress naturalized all such future children in 1934, but only *IF* the mother meets age and residency conditions.
Natural born citizens do not have conditions placed on their citizenship, or that of their mother.
Actually, there are a whole lot of conditions place on the citizenship of natural born citizens. One condition is being born on US soil (title 8 section 1401 subsection A) or being born outside of the US to parents who are both citizens (title 8 section 1401 subsection C). Further conditions apply including conditions by which a natural born citizen might forfeit their citizenship.
All governed by LAW
All set in place by Congress
As specifically enumerated in the Constitution