CORS error while trying to run an AWS lambda function

I’m trying to run a lambda function from my front-end website but I keep getting a CORS error.

The front-end code that should contact the lambda function is the following:

    const handleSubmit = async (e) => {
        e.preventDefault();
        setIsSubmitting(true);
        setSubmitMessage('');

        try {
            const response = await fetch('https://foobar.lambda-url.eu-west-2.on.aws/', {
                method: 'POST',
                headers: {
                    'Content-Type': 'application/json',
                },
                body: JSON.stringify(formData),
            });

            if (response.ok) {
                setSubmitMessage('Your request has been submitted successfully!');
                setFormData({
                    name: '',
                });
            } else {
                throw new Error('Form submission failed');
            }
        } catch (error) {
            console.error('Error:', error);
            setSubmitMessage('An error occurred. Please try again later.');
        } finally {
            setIsSubmitting(false);
        }
    };

The error is the following:

Access to fetch at 'https://foobar.lambda-url.eu-west-2.on.aws/' from origin 'https://my-website.amplifyapp.com' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: 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.Understand this error
index.js:29 
        
POST https://foobar.lambda-url.eu-west-2.on.aws/ net::ERR_FAILED

index.js:50 Error: TypeError: Failed to fetch
    at index.js:29:36

CORS are active on AWS. The thing that I find strange is that the request on the chrome network tab display “Provisional Header are shown”:

And if I use the same parameter but using the terminal and curl the call goes through without any problem, for example:

curl -X POST 'https://foobar.lambda-url.eu-west-2.on.aws/' 
-H 'Content-Type: application/json' 
-d '{"name":"test test"}'

Here’s the lambda function:

import { SES } from "@aws-sdk/client-ses";
const ses = new SES({ region: 'eu-west-2' });

export async function handler(event) {
  if (event.httpMethod === "OPTIONS") {
    return {
      statusCode: 200,
      headers: {
        "Access-Control-Allow-Origin": "*",
        "Access-Control-Allow-Headers": "Content-Type",
        "Access-Control-Allow-Methods": "POST, OPTIONS",
      },
      body: JSON.stringify({ message: "Preflight check successful" }),
    };
  }

  let formData;

  if (event.body) {
    try {
      formData = JSON.parse(event.body);
    } catch (error) {
      console.error("Error parsing event body:", error);
      return {
        statusCode: 400,
        headers: {
          "Access-Control-Allow-Origin": "*",
        },
        body: JSON.stringify({ message: "Invalid JSON" }),
      };
    }
  } else {
    return {
      statusCode: 400,
      headers: {
        "Access-Control-Allow-Origin": "*",
      },
      body: JSON.stringify({ message: "No body provided" }),
    };
  }

  const params = {
    Destination: { ToAddresses: ["my-email-address"] },
    Message: {
      Body: { Text: { Data: JSON.stringify(formData, null, 2) } },
      Subject: { Data: "form info" },
    },
    Source: "some-user",
  };

  try {
    await ses.sendEmail(params);

    return {
      statusCode: 200,
      body: JSON.stringify({ message: "Email sent successfully" }),
    };
  } catch (error) {
    console.error(error);
  } finally {
    console.log("finished");
  }
}

What am I missing?