In the 2005 screenplay, Alma is cooking greasy hamburger, when Ennis returns to find a postcard waiting for him.
However, in the 2003 and 2004 screenplays, Alma was cooking chicken fried steak. The meat was changed after Annie Proulx made it clear that chicken fried steak was not a common meal in Wyoming.
In the movie, we cannot tell what she's cooking, and Ennis doesn't really care anymore.