And this is very easily answered with a thought experiment:
Imagine yourself as a character in a book, video game, or movie. You have figured out enough of the world/universe you live in to extrapolate back to a point where the book "starts", and may even figure out that it will have an "ending". However, the Author of the book predates the existence of the book. In fact, one of the first things the Author created was the concept of Time itself, which is why when you go back to the first second of the Big Bang, you can only go back so far before the laws of physics fall apart. So here, the Evangelical Athiest has to pretend to not understand that since the Author created time itself, there could not be a "time" before the Author, and hence a beginning of the Author. The Author is outside the natural world (the book we inhabit), and is, by definition, supernatural.