Generally food/dishes from different cultures that are prepared in a more palatable way for "white people" which end up lacking, in spices, unique ingredients, flavors or preparation methods that are signatures of that type of cuisine or dish (orange chicken, beef and broccoli, California rolls). Or traditional "American" food that is not known to have a lot of distinct flavors (fish sticks, meatloaf, turkey).
White People Food does not necessarily need to be made by white people or preferred by white people but is more of a critique that the food is bland and not authentic to it's cuisine by people from that culture or familiar with the
food of that culture.
Joe: My tacos are super good right?
Miguel: I love you man...but it's just ground beef, refried beans, iceberg lettuce and salsa from a jar. It's white people food bro.