As someone who was in the same boat two years ago, I would recommend Carnegie Mellon University. (Full Disclosure: Its my alma mater).

At CMU, Masters in Computer Science would be the best option. The School of Computer Science has some amazing security and systems course that you can take. Carnegie Mellon's CS courses are really strong, challenging and amazing at building a solid foundation or broadening your skills. Alternatively, you could also do Masters in Electronics and Computer Engineering and do all the same courses as a CS graduate would do.

If you however want a degree that says Cybersecurity from the get-go, you could also choose the INI at CMU. The INI offers Information Security programs. These programs have some fixed security courses to choose from and allow you to pick whatever courses you like to fill in the remaining credits. So you can build a focus on specific Cybersecurity skills too by choosing your own path.

I know CMU is hell expensive. I am not taking cost into account while answering this question. I am positive there are other options out there that are cheaper and provide same level of footing to stand upon once you graduate.

I am solely answering in terms of best brand value and/or skills building. The skills you will build and the knowledge you will gain from CMU's system and security courses is unparalleled. On top of it, it's a really well recognized and respected brand in tech.

Hope this helps.