結構めんどうだったのでメモ

$ aws cloudformation describe-stacks\
 --region リージョン\
 --profile プロファイル\
 --stack-name "スタック名"\
 --output text\
 --query 'Stacks[].Outputs[?OutputKey==`Outputsのキー`].[OutputValue]'

--queryに指定している値は、--queryオプションなしで--output jsonで出力してから作りました。

$ aws cloudformation describe-stacks\
 --region us-east-1\
 --profile xxxxxxxxxxxx\
 --stack-name "xxxxxxxxxxxx"\
 --output json
{
    "Stacks": [
        {
            "StackId": "arn:aws:cloudformation:us-east-1:xxxxxxxxxxxx:stack/xxxxxxxxxxxx/xxxxxxxxxxxx",
            "StackName": "xxxxxxxxxxxx",
            "ChangeSetId": "arn:aws:cloudformation:us-east-1:xxxxxxxxxxxx:changeSet/xxxxxxxxxxxx/xxxxxxxxxxxx",
            "Parameters": [
                {
                    "ParameterKey": "Env",
                    "ParameterValue": "dev"
                }
            ],
            "CreationTime": "2020-12-15T06:25:42.183Z",
            "LastUpdatedTime": "2020-12-15T06:25:53.614Z",
            "RollbackConfiguration": {},
            "StackStatus": "CREATE_COMPLETE",
            "DisableRollback": false,
            "NotificationARNs": [],
            "Capabilities": [
                "CAPABILITY_NAMED_IAM"
            ],
            "Outputs": [
                {
                    "OutputKey": "xxxxxxxxxxxx",
                    "OutputValue": "xxxxxxxxxxxx",
                    "Description": "xxxxxxxxxxxx"
                }
            ],
            "Tags": [],
            "EnableTerminationProtection": false,
            "DriftInformation": {
                "StackDriftStatus": "NOT_CHECKED"
            }
        }
    ]
}

参考：https://docs.aws.amazon.com/cli/latest/userguide/cli-usage-output.html