Soak the red onion in a bowl of water with a sprinkle of salt for about 10 minutes to mellow its flavor.

Prepare the aji amarillo by carefully deseeding it and chopping it finely.

Combine the soaked, drained onion, finely chopped aji amarillo, and cilantro in a mixing bowl. Stir together gently.

Add the freshly squeezed lime juice to the mixture and stir well to ensure everything is well-coated.

Season with salt to taste and adjust as needed.

Optional: Serve immediately or let the salsa chill for 30 minutes to deepen the flavors.