I am the last person to have any desire to defend Cruz, but yes, he was born in Canada to a mother with U.S. citizenship
His mother's citizenship is questionable.
I haven't found anything that shows that it has been verified that she is a citizen of the United States.
There are statements that she was a citizen of Canada when Cruz was born.
and a father with Cuban citizenship. He had dual citizenship, deriving his U.S. citizenship through his mother, until a couple years ago when he realized that his Canadian citizenship might be a drag on his presidential ambitions, so he then renounced it.
Having a dual citizenship and a foreign national for a parent does disqualify him, just like Obama should have been disqualified for the exact same reason.
Those things make is so he does not meet the "natural born citizen" requirement, even if he is can be considered a native-born citizen.
The reason for the requirement was to ensure that the president would have no foreign citizenship ties that could interfere with his leadership of the United States.
Both Obama and Cruz have foreign citizenship ties because their fathers were foreign nationals, not citizens of the United States, so neither is qualified to be president.