Chilean salad, or 
ensalada chilena is a 
traditional Chilean food that you will encounter during your stay in Chile.
Here’s a Chilean salad next to some freshly eaten seafood: 
If you are used to a salad with lots of lettuce and green color, you may not even think that 
ensalada chilena qualifies as a salad.
However, this salad variation consisting primarily of tomatoes, onions, and cilantro is a common side dish with Chilean meals.
There are many different recipes but the basic ingredients are:
3 sliced tomatoes
1 sliced onion
1/4 cup diced cilantro
1 tablespoon oil
Salt, vinegar, pepper to taste.
Here's another persons experience and recipe for Chilean Salad.  Doesn't her picture below look delicious?:

I  will never forget the first time I ordered “Chilean Salad” back as an  exchange student. Expecting a heaping bowl of greens, to my dismay, what  arrived was a simple plate of peeled tomatoes, onions, and cilantro.  The waiter, sensing my confusion, quickly explained that the term  “salad” in Chile is a generic term for any fresh vegetable, raw or  cooked, served cold as an accompaniment.  And in this case, Chilean  salad was always made with tomatoes. Aha!.
This salad is a staple on every Chilean table. I am sure if you polled  any Chilean, they would name this as a perennial favorite. Quite simply  it goes with everything. From the classic 
humitas, sweet corn tamales, and corn pie in the summer time to 
costillar de cerdo, spicy pork ribs, grilled chicken, fried fish, any 
asado, barbecued  beef, or even as a side with empanadas or beans which Chileans love.  The freshness of the tomatoes, mildness of the onions, and the herbs  create crunchy, juicy, tangy, herby ecstasy in your mouth.
Cecilia, my mother-in-law, taught me the age-old Chilean trick of  tempering the onions with salt or sugar to take away their sting so they  can be savored raw in the salad. Although many Chilean cooks would add  cilantro to this recipe, basil is so abundant in the summer time and  pairs so well with ripe, succulent tomatoes, I have taken the liberty of  making that substitution.
1 medium onion or red onion
1 teaspoon of salt or sugar
3 large ripe tomatoes
¼ cup basil cut in threads, or chopped cilantro
1 tablespoon olive oil
1 teaspoon red wine vinegar
Sea salt to taste 
1/8 teaspoon black pepper
Slice the onion paper-thin, cutting with the grain (lengthwise).  Separate the sections with your fingers. To temper, sprinkle a teaspoon  of salt or sugar, combine well with your hands to mix. Set aside for 30  minutes.
In the meantime, peel, slice, and arrange the tomatoes on a platter.  If you prefer, you can leave the skins on the tomatoes although  traditionally, most Chileans will peel them.Cut the basil in threads by rolling the washed leaves up like a cigar  and slicing finely. When the onion has rested and rendered its “milk,”  rinse it well with cold water and gently squeeze out the excess liquid.  Arrange the onions on top of the tomatoes and sprinkle with the basil  threads.Drizzle with olive oil and red wine vinegar. Season with salt and pepper. Lightly toss before serving.   
Serves 4-6 as a side.