Mock Postman request using axios is returning string instead of object

Question

I have created a Postman mock server. I am calling the server in my web application using axios as below:

const response = await axios.get(`${BASE_URL}/products`, {
    'headers': {
        'Content-Type': 'application/json'
    }
});
const axiosData = response.data;
return axiosData.data;

Weirdly axiosData is a string! Therefore axiosData.data which contains the actual data from the response is undefined.

How can I get my Postman mock server to return axiosData as JSON?

Note: I have also set a response header: Content-type: application/json for my response in Postman.

Edit:

This is the response I get back from the mock server (which is string):