Hi @paulwwstorm
Welcome to Terraform forums, it is a great technology for infrastructure.
Take a look at the following question about executing commands after infrastructure creation:
There is a Terraform provider for Kubernetes that you could use, but I would suggest that you write a different Terraform definition for that, as your GKE should have a longer and different life than the ingress app:
https://www.terraform.io/docs/providers/kubernetes/index.html
So actually not a single Terraform apply.