Locating the actual Dockerfile instructions

According to the AWS documentation on this [page](https://docs.aws.amazon.com/lambda/latest/dg/ruby-image.html) , I expected to see instructions within the [Dockerfile](https://github.com/aws/aws-lambda-base-images/blob/ruby3.3/Dockerfile.ruby3.3) that would indicate how exactly it was built.

Since it is based on AL2023 Minimal, I expected the Dockerfile to start with `FROM amazonlinux:2023-minimal`, with commands to install Ruby, etc. Instead it is based on `FROM scratch` and I see there are some included xz files, but I'm having trouble extracting those locally.

Can you help point me in the right direction?

Thanks