指定的方法标识符无效(服务:AmazonApiGateway;状态代码:404;错误代码:NotFoundException)

我正在尝试创建一个API方法,如:

ApiIndex:
  Type: AWS::Serverless::Function
  Properties:
    Handler: src/apis/index.handler
    FunctionName: !Sub '${ProjectName}-api-index'
    Role: !GetAtt LambdaExecutionRole.Arn

ApiIndexMethod:
  Type: AWS::ApiGateway::Method
  Properties:
    HttpMethod: ANY
    AuthorizationType: NONE
    Integration:
      Type: AWS_PROXY
      IntegrationHttpMethod: GET
      Uri: !Sub arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${ApiIndex.Arn}/invocations
    OperationName: Index
    ResourceId:
      Fn::ImportValue:
        !Sub ${BaseStack}-apiroot
    RestApiId:
      Fn::ImportValue:
        !Sub ${BaseStack}-api

但我得到了:

指定的方法标识符无效(服务:AmazonApiGateway;状态代码:404;错误代码:NotFoundException)

Resources:
  Api:
    Type: AWS::ApiGateway::RestApi
    Properties:
      Description: !Sub ${ProjectName} API gateway
      EndpointConfiguration:
        Types:
          - REGIONAL
      Name: !Ref ProjectName


Outputs:
  Api:
    Description: API gateway
    Value: !Ref Api
    Export:
      Name: !Sub ${AWS::StackName}-api

  ApiRootResourceId:
    Description: API Gateway root resource ID
    Value: !GetAtt Api.RootResourceId
    Export:
      Name: !Sub ${AWS::StackName}-apiroot