In a large bowl, place the avocados, tomatoes, onion, cilantro, serrano, lemon juice, and salt, to taste. Stir gently until well combined. Transfer to a serving bowl and serve. Note: To keep the guacamole from turning brown, press a pit from one of the avocados into the center of the dish. Remove before serving. enjoy! ? Now here is how to freeze avocados! Just cut in half and remove the seed. Wrap in saran wrap (a vacuum sealer is the best option if you have one) then place into a freezer safe container or ziploc bag. I usually keep mine no longer than 3 months. thaw at room temperature and enjoy as guacamole, topping for fajitas or tacos.