Atheist asked who created God (الله). This question exhibits ignorance. God would not be God if God were created. God would be part of the creation as he would be created. Something within the universe. Bound by space-time like everything else that is created.
SAHIH International –
3:2 Allah – there is no deity except Him, the Ever-Living, the Sustainer of existence.
Arabic: اللَّهُ لَا إِلَٰهَ إِلَّا هُوَ الْحَيُّ الْقَيُّومُ
Note: The word “he” is being used in the generic sense. God (الله) has no gender or sex.