Oaxaca's ancient stone soup, where river-heated stones cook fish, shrimp, and vegetables in a gourd bowl. This healthy, protein-rich ceremonial dish represents one of Mexico's oldest family cooking traditions.
Prepare all the fish and shrimp by cutting into bite-size pieces, keeping them chilled until ready to cook.
In a large heatproof ceramic or metal bowl, layer fish, shrimp, tomatoes, onion, red bell pepper, jalapeño, and half of the cilantro.
In a separate pot, heat water with sea salt, black pepper, and oregano until it comes to a rolling simmer (~5 minutes on medium-high heat).
Carefully pour the seasoned hot water over the layered ingredients in the bowl, gently mixing to distribute the heat and seasonings.
If using stones: Preheat smooth river stones over an open flame or in the oven at the highest setting for 30-45 minutes, then, using tongs, transfer the hot stones into the bowl to rapidly cook seafood and vegetables (alternatively, keep the bowl over low heat if not using stones).
Let the soup rest uncovered for 7-10 minutes, allowing the fish and shrimp to cook through till just opaque, then remove stones (if used).
Serve immediately, garnished with reserved chopped cilantro and fresh lime slices.