Final answer:
Use the TrackDependency API method to monitor the performance of an app accessing an Azure Redis Cache and its impact on app response time.
Step-by-step explanation:
To monitor the performance of an app accessing an Azure Redis Cache and its impact on the app's response time using Azure Monitor, you should use the TrackDependency API method. The TrackDependency method is designed to log interactions that your application has with external components such as databases, file systems, or caches like Azure Redis Cache. By utilizing this method, you can record how long these dependencies take to execute and how they affect overall response times.