Entity Framework is an object-relational mapping (ORM) framework that abstracts the database interactions in ASP.NET Core applications. It allows developers to work with database entities using object-oriented programming concepts, eliminating the need to write raw SQL queries. This simplifies data access code, improves productivity, and reduces the likelihood of errors.

A scalable web application architecture with ASP.NET Core and Entity Framework typically includes components such as a presentation layer (MVC or Razor Pages), a business logic layer (services), a data access layer (Entity Framework), and a scalable infrastructure (cloud hosting, load balancers, etc.). Additionally, it often employs asynchronous programming, caching mechanisms, and distributed caching for improved scalability.

Dependency injection (DI) is a design pattern in which dependencies are injected into a class rather than created internally. In ASP.NET Core, DI is built into the framework and is used to provide services to components throughout the application. DI promotes loose coupling, which improves code maintainability, testability, and scalability by making it easier to replace or update dependencies without modifying existing code.

Performance optimization strategies for ASP.NET Core applications with Entity Framework include implementing efficient database queries, using data caching, enabling compression and minification of resources, leveraging asynchronous programming, and optimizing network requests. Additionally, monitoring and profiling tools can help identify performance bottlenecks for further optimization.

Common challenges include managing stateful components in a stateless environment, handling concurrency and data consistency, designing efficient database schemas, and orchestrating microservices. These challenges can be addressed through careful architectural planning, implementing best practices, utilizing appropriate design patterns, and leveraging cloud services for scalability and resilience.

ASP.NET Core provides features such as built-in support for Docker containers, HTTP/2 support, and integration with Kubernetes for orchestrating microservices. Microservices architecture enables applications to be broken down into smaller, independent services that can be developed, deployed, and scaled individually, offering benefits such as improved scalability, flexibility, and maintainability.

Best practices for deploying and hosting ASP.NET Core applications include containerization using Docker for consistency and portability, utilizing cloud platforms like Azure, AWS, or Google Cloud for scalable infrastructure, implementing continuous integration and deployment (CI/CD) pipelines for automated deployments, and monitoring application performance and scalability metrics in production environments.

Security measures for ASP.NET Core applications with Entity Framework include implementing authentication and authorization using ASP.NET Core Identity or OAuth, validating and sanitizing user input to prevent SQL injection and cross-site scripting (XSS) attacks, enabling HTTPS for secure communication, and regularly updating dependencies to patch security vulnerabilities.

Recommended tools and frameworks include Redis or Azure Cache for distributed caching, Serilog for structured logging, Swagger for API documentation, AutoMapper for object-to-object mapping, Polly for resilience and transient fault handling, and SignalR for real-time communication. These tools and frameworks can help enhance the scalability, performance, and maintainability of ASP.NET Core applications with Entity Framework.