The cilantro-lime dressing is key to this delicious salad.

1/2 medium red onion, thinly sliced

2 tablespoons plus 1/4 cup freshly squeezed lime juice, from about 3 limes

2 teaspoons sugar

Coarse salt

1 jalapeno chile (seeds and ribs removed for less heat, if desired), chopped

1 cup lightly packed cilantro leaves

1/2 cup olive oil

4 avocados, about 8 ounces each, thinly sliced

In a small bowl, combine onion with 2 tablespoons lime juice, 1/2 teaspoon sugar, and 1/4 teaspoon coarse salt; toss to combine. Let lime-marinated onion sit at room temperature until it softens and brightens in color, about 1 hour (up to 1 day, covered and refrigerated).
Make dressing: In a blender, combine remaining 1/4 cup lime juice, jalapeno, cilantro, and remaining 1 1/2 teaspoons sugar; season generously with salt. Blend until smooth. With the motor running, add oil in a steady stream through the feeder opening until incorporated.
Just before serving, slice avocados; arrange on a serving plate. Top with onion; drizzle with dressing.