Hosting frontend and backend on two different Heroku domains

I made a full-stack web application with React and Express as part of my portfolio projects. I tried publishing it on Vercel and Heroku (tried Netlify also) but unfortunately, I learned that sending cookies between two different domains is not possible. The next thing I tried, is to host both on Heroku (e.g: & which, unfortunately, does not work also.

What else do I need to do? I am still learning how to deploy properly so I might miss out on some workarounds. Advice is greatly appreciated.

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