Gail fixed your code, but I'll explain a little:

A CTE is really nothing more than a temporary view. Because of that, it acts just like a view when you interact with it. This means you can SELECT, INSERT, UPDATE, and DELETE against the CTE (with some oddities.)

If you UPDATE the CTE, it will work as long as you don't attempt to UPDATE multiple underlying tables. If you do, you'll get a very nice error message telling you exactly what you did wrong. (Coincidentally, it's one of my favorite error messages for this reason.) You'll get the same thing if you attempt to INSERT into the CTE and define columns from multiple tables. You can't DELETE from a multi-table CTE at all (same error message.)

Msg 4405, Level 16, State 1, Line 1

View or function 'dbo.JK_Test_View_2' is not updatable because the modification affects multiple base tables.

You CAN, however, do any of the above against a CTE if it includes derived columns (COUNT, SUM, ROW_NUMBER, etc) from a single table. This makes a CTE very nice for deduplicating data - you can use ROW_NUMBER to look for rows with duplicate keys, and then DELETE where the ROW_NUMBER > 1. This gets around the inability to use window functions such as ROW_NUMBER() in the where clause.