A cloud computing platform and infrastructure for building, deploying and managing applications and services through a worldwide network of Microsoft-managed datacenters.
The free version of Defender for Cloud has a nice set of built-in recommendations. The full version provides more detailed assessments and compliance monitoring. Assuming you want the stay on the Microsoft stack:
Defender for Endpoint - Endpoint and antivirus protection
Defender for Cloud - Azure resource and server endpoint management
Defender for Office - All things M365
Defender for Cloud Apps - CASB and cloud service controls
Defender for Identity - Bring on-premise identity protection into the cloud
Azure Active Directory Identity Protection - Protecting AAD identities
Sentinel is the cherry on top that brings them all together along with any other security logs and signals.