How to demonstrate your security posture improvement
Azure Security Center (ASC) uses the Secure Score feature to help you assess the security of your Azure environment. It provides a single percentage value that represents the security of your Azure resources and offers recommendations of how your security posture can be improved.
Although the Secure Score is a very useful indicator at any single moment, it can be helpful to show improvement over a given period of time. ASC includes sample workbooks which includes a Secure Score Over Time template. This workbook provides a visual representation of historical values of Secure Score.

Other useful sample workbooks are supplied which are easily customised to create meaningful dashboards to help understand your security vulnerabilities.