How to run Cloud Formation Init commands in PowerShell and not cmd?

In Coudformation templates, there is a section to specfiy commands like below. Under fullServer I am running the command install. However, when I look at the logs after cfn has run on the server, it shows

2022-10-20 13:41:25,780 [INFO] Command install succeeded
2022-10-20 13:41:25,796 [DEBUG] Command install output: $MAGIC

This is because the $Magic is how to declare and use variables in powershell where as cmd needs the set keyword. I would expect the output of this command to be Command install output: I am from the full server env.

"AWS::CloudFormation::Init": {
                "configSets": {
                    "downloadS3Data": ["downloadS3"],
                    "Full": [{"ConfigSet": "downloadS3Data"}, "fullServer"],
                    "default": [ {"ConfigSet": "Full"}],
                    "App": [{"ConfigSet": "downloadS3Data"}, "appServer"],
                    "Interface": [{"ConfigSet": "downloadS3Data"}, "interfaceServer"],
                    "Notification": [{"ConfigSet": "downloadS3Data"}, "notificationServer"]
                },
                "downloadS3": {
                    "files": {
                        "C:\\ccw_downloads\\test.txt": {
                            "source": "https://ccw-to-rds-poc-1.s3.us-east-2.amazonaws.com/test.txt",
                            "authentication": "S3AccessCreds"
                        }
                    }
                },
                "fullServer": {
                    "commands": {
                        "install": {
                            "command": "echo $MAGIC",
                            "env": {"MAGIC": "I am from the full server env"},
                            "cwd": "C:\\ccw_downloads",
                            "waitAfterCompletion": 120
                        }
                    }
                }
             }

I would like to run the command with PowerShell and not cmd. Is there a way to specify that like I can with User Data?

I know that I could append PowerShell -Command to the beginning, making cmd call PowerShell and pass args. However, that would not allow me to use the enviornment variable MAGIC. For example "command": "Powershell -Command 'echo $magic'"