How do you enable SQL Server 2019's result set caching?

Currently, in CTP 2.3, in so far as I can tell - you cannot enable this, even under DAC.

This is a feature available only in Azure Synapse Analytics.

When you create your database using CREATE DATABASE DBName (EDITION = 'DataWarehouse'), you will be able to use ALTER DATABASE DBName SET RESULT_SET_CACHING ON.

Quote from Azure Synapse Analytics release notes:

When result set caching is enabled, query results are automatically cached in the user database for repetitive use. This allows subsequent query executions to get results directly from the persisted cache so recomputation is not needed. Result set caching improves query performance and reduces compute resource usage. In addition, queries using cached results set do not use any concurrency slots and thus do not count against existing concurrency limits. For security, users can only access the cached results if they have the same data access permissions as the users creating the cached results. For more information, see Performance tuning with result set caching. Applies to version 10.0.10783.0 or higher.

Here is the documentation page for ALTER DATABASE on Azure Synapse Analytics.