In a large bowl, place the avocados, tomatoes, onions, cilantro, serrano, lemon juice, and salt. Stir gently until well combined.
Transfer to a serving bowl and serve.
To keep the guacamole from turning brown, press a pit from one of the avocados into the center of the dish. Remove it before serving.
Reprinted from Eva's Kitchen by Eva Longoria. Copyright (c) 2011 by Eva Longoria. Photographs copyright (c) 2011 by Ben Fink. Published by Clarkson Potter, a division of Random House, Inc.