At and by birth, or at and by statute? Cruz is a US citizen by naturalization statute.
We've been over this several times already, so don't pretend you haven't heard it before.
Obviously the Framers of the Constitution believed that, in accordance with past practice in the common law, the legislature had the power to specify exactly who, born outside of the country, was to be considered a natural born citizen (and thus eligible to the Presidency).
Because the First Congress and First President, which included 40% of the Signers of the Constitution, did exactly that.
And of course Bayard, and Chief Justice John Marshall ("The Great Chief Justice") agreed that persons in Cruz's situation WERE ELIGIBLE.
All of this means that your desire for Ted Cruz not to be eligible, is hogwash.