A record-triggered flow is the preferred declarative automation. Salesforce supports record-triggered automation when records are created, updated, or deleted, and its current Flow architecture includes after-delete processing for actions that must occur because a record was removed. The flow can trigger from Task deletion, use information from the triggering Task to identify the related Case, obtain the Case owner, and execute the email notification action. Assignment rules are designed primarily for assigning records such as Cases or Leads and do not respond to Task deletion. Escalation rules manage Case escalation timing, not deletion events. An Apex trigger could technically implement the requirement, but Platform App Builder principles favor native declarative automation when Flow supports the event and required action.

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