Follow the steps in order for the best result.
In a large pot, combine the beef, chopped onion, and salt. Add water to fully submerge the ingredients. Bring the mixture to a boil, then reduce the heat to medium-low. Simmer for approximately 1 1/2 to 2 hours, or until the beef is very tender. Once cooked, remove the beef from the pot, making sure to reserve the flavorful stock for future use in soups or other recipes. Allow the beef to cool slightly, then shred it into small pieces using your fingers.
In a large bowl, prepare the marinade by whisking together the olive oil, vinegar, dried oregano, salt, and pepper. Add the chopped tomatoes, thinly sliced onion, and chopped chilies to the bowl. Toss the vegetables gently to coat them with the marinade. Set the mixture aside for a few minutes, allowing the flavors to meld and the vegetables to marinate.
Gently combine the shredded beef and chopped avocados with the marinated vegetables. Taste and adjust the seasoning as needed. Arrange the salad on a serving platter and serve chilled or at room temperature. This delightful dish pairs perfectly with warm tortillas.
Variations: Salpicón can also be made with chicken (salpicón de pollo), seafood (salpicón de mariscos) or tuna (salpicón de atún).
Other possible additions: chopped lettuce, chopped cucumbers, olives, pickled jalapeños.
Garnish with lime wedges, cilantro and crumbled queso fresco if you like.
Substitute sour orange juice or lime juice for the vinegar for a more tropical flavor.