You are asking about an exclamatory sentence that is in Taglish form.
Normally, a ma- adjective formulation (maganda, malaki, malinis, mapangit, magulo, mataas, matalino, mababa, mahaba, maingay, etc.) is converted to an exclamation by replacing the ma- prefix with ang followed by the root word of the adjective.
Malaki ang bahay nila (Their house is big) converts to the exclamation Ang laki ng bahay nila!
Matalino ang anak niya (Her child is intelligent) converts to the exclamation Ang talino ng anak niya!
Thus, the "original" of your Taglish sentence is Cute ka (You are cute) which converts to the exclamation Ang cute mo!
Note that your Taglish sentence also uses the method of intensification by repetition, ang cute-cute mo. The same formulation applies in Tagalog as in Ang ganda-ganda niya, Ang laki-laki ng bahay nila, Ang linis-linis ng kotse niya, etc.
