从JS Fetch访问AWS API Gateway→Lambda时遇CORS问题求助

社区里相关问题不少，但我试了各种方法都没解决。情况如下：我在AWS API Gateway后部署了Node.js Lambda，用Postman调用完全正常，但在简单的HTML+JS网站中使用fetch调用时，触发了CORS错误：

Access to fetch at 'https://......' from origin 'https://......' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

我已尝试的解决措施：

• 创建Lambda函数URL，排除API Gateway的复杂性
• 添加OPTIONS请求处理器，该处理器可正常工作且已配置对应CORS头
• 在响应输出中添加以下CORS头，且能在Postman的响应中看到：

{
  "Content-Type":"application/json",
  "Access-Control-Allow-Headers" : "Content-Type,Authorization,X-Amz-Date,X-Api-Key,X-Amz-Security-Token",
  "Access-Control-Allow-Origin": "*",
  "Access-Control-Allow-Methods": "OPTIONS,POST,GET"
}

内容的提问来源于stack exchange，提问作者Ash