I leave it to the Cubans to decide who is or is not a natural born citizen of Cuba. It is none of my business what they do.
A child cannot be a natural born citizen of a country they are not born in.
The definition of a natural born citizen is that the person is a citizen automatically because the child is born in the country of parents who are citizen of that country, no statutes are required. In the case of Ted Cruz he might possibly be a citizen but only by act of naturalization.
The dictators there probably aren't concerned with such concepts anyway. They took and keep power using raw armed power.