I have always reasoned thus: God created the universe. The definition of "universe" is "everything that exists." In order for God to have performed the many feats attributed to him, he obviously must exist. Therefore, God is part of the universe. Therefore, God created himself. This is a logical fallacy. Therefore, either (1) God does not exist, or (2) God did not create the universe. Your suggestion that God and the universe came into existence at the same moment is consistent with conclusion #2. It is logically possible that, although God did not create the universe, he came into existence as a singularity at the same moment as the emergence of the universe (or for that matter some arbitrary span of time later): a sentient creature with unique powers and various other astounding characteristics such as immortality. Of course at this point the Rule of Laplace must be invoked. We must be presented with extraordinary evidence to support the extraordinary assertions attributed to God, before we are obliged to treat them with respect. To date, the best evidence anyone has ever submitted is a tortilla, out of millions fried every year, with a scorch mark that is said to be the image of a person mentioned in the Bible, of whom no portraits survive against which to compare it.