Realistic options are limited but 2 things I can think of.
Begin the uturn from the inside of the lane. Gives the car as much room as possible to avoid a hit and pass but makes the uturn harder.
Good old fashion hand signals. - Don't make a last second decision to uturn, know ahead of time and notify/alert others of your intent before you turn.
Even if the driver behind you don't know what it means, "hopefully" it will get their attention but don't bet your life on it.