It's possible to use EventBridge event "CloudFormation Resource Status Change" to execute code when the CloudFormation stack itself is created. 

This can be done describing the EventBridge event rule for a Lambda function that match the emitted event:

StackEvent:
  Type: EventBridgeRule
  Properties:
    EventBusName: default
    Pattern:
      source:
        - aws.cloudformation
      detail-type: 
        - CloudFormation Stack Status Change
      detail:
        stack-id:
          - !Ref AWS::StackId
        status-details:
          status:
            - CREATE_COMPLETE

The event rule pattern is interpolated with AWS::StackId pseudo parameter reference.

So far the only status change that is reported is CREATE_COMPLETE.

Here a GitHub gist with a CloudFormation (SAM) example template: https://gist.github.com/daaru00/d5443e5de9b25fd7ee637e6d6a22d137