"This ceviche recipe is from my husband's family from Peru. The ceviche is made with salmon, shrimp, and of course, lots of lime juice. You can substitute other fish, like tilapia, as well. Use fewer chile peppers (or remove the seeds) if you don't like it too spicy. In Peru, it is generally eaten with sweet potatoes."
Combine salmon and shrimp in a large glass bowl. Combine 2 quarts water and 1/4 cup sea salt; stir until salt has dissolved. Pour salt water over salmon and shrimp and set aside for 30 minutes.
Mix onions and remaining 1/4 cup sea salt in a bowl and cover with remaining cold water. Set aside for 15 minutes. Drain.
Combine lime juice, celery, ginger, garlic, and chile peppers in a blender; blend until smooth. Strain mixture through a sieve.
Rinse salmon and shrimp in a sieve under running cold water to wash off the salt. Rinse red onions. Mix salmon, shrimp, and onions in a large bowl. Cover with lime mixture. Set aside for 30 to 40 minutes. Serve garnished with fresh cilantro, lettuce leaves, and lime wedges.