The natural universe appeared from nothing.

Since the universe is all that naturally exists (matter, energy, forces, space and time) whatever the first case was must have been super-natural.

Since the universe hasn't always existed, the first cause couldnt have been in operation eternally but was the chosen action of a free agent.

Since the universe is massively large and full of unimaginable energy, the first cause must have been unimaginably powerful.

Since the universe is finely-tuned to support matter, energy, life, etc, the first cause must have been immensely intelligent.

Since the first cause created time, the first cause must itself exist in an eternal state.

So, the first cause (or Creator) of the universe was a super-natural, personal, Omnipotent, Omniscient and eternal Being. That's God.