A simple challenge for atheists

[Esquilax]

For the purposes of this argument, God did not begin to exist and is someone who could create a universe out of nothing.

Which I think is the biggest flaw with the cosmological argument, the way it's willing to bend on every detail of god's existence except the parts that allow it to solve the problem the argument demands must exist. It's the most obvious sign that what you're doing here isn't meant to lead to a proper conclusion based on evidence, but to the god conclusion specifically, because it's so damn convenient that here's your argument, and oh look, here's an answer that just happens to have exactly the properties required to deal with that and nothing else!

Strip away all the nouns and details, and what you're essentially saying is "here's the thing that solves the problem that my argument asserts to exist by fiat." You're demanding that a god-shaped hole exists in the universe, without providing any evidence, and then putting on a big show of considering an answer before pulling a pre-fabricated god shaped piece out from behind your back and acting like you never had that in mind beforehand. You're formulating your problem to fit the solution you want.