Do you want to write secure ASP.NET Core applications and do you want to know how to protect your single page application? One of the best places to learn about security is the the blog of Damien Bowden.
Damien is a Microsoft MVP since 2016, living in Switzerland and very interested in web development, application security and Azure. He is pretty involved, encouraged and well known in the .NET community.
Damien: "My favourite technologies are ASP.NET Core, OpenID Connect, OAuth, SQL, EF Core, Angular, Typescript."
His Blog is full of very detailed and deep-dive posts about ASP.NET Core Identity, Identity Server, OAuth, OpenID Connect. Besides blogging he is also speaking on Meetups, user groups and conferences. He is involved in many open source projects, including Microsoft's projects on GitHub.