Ingredients
For the Brisket
3 dried pasilla chiles
3 dried ancho chiles
3 dried guajillo chiles
4 medium plum tomatoes (about 1 pound), cored, seeds removed and roughly chopped
1/2 medium white onion, peeled and roughly chopped
2 medium garlic cloves, peeled and roughly chopped
2 1/2 teaspoons of kosher salt, plus more as needed
1 brisket (4-5 pounds)
For the Rhubarb Sauce
2 large rhubarb stalks cut into 1/2-inch pieces (about 2 cups)
1/3 cup granulated sugar
1/4 cup water
For Serving
Small (6-inch) corn tortillas, warmed
Chopped fresh cilantro
Directions
Place the pasilla, ancho and guajillo chilis in a medium saucepan and cover with water by a couple of inches (the chilies will float to the top). Set the saucepan over high heat, bring to a boil, and continue boiling until the chiles are soft, about 15 minutes. Drain and let cool to the touch.
Wearing gloves, open each chile and remove the veins and seeds. Place the chile flesh and skin in a blender along with the tomatoes, onion, garlic, salt and 3 cups of water. Blend until smooth, then taste and add more salt, if needed.
Place the brisket in a large baking dish or roasting pan, cover with the chile salsa, then cover tightly with aluminum foil. Refrigerate for at least 2 hours or up to overnight.
Heat the oven to 325 F. Place the brisket in the oven and cook for 2 hours. Remove the baking dish, carefully flip the brisket over, and continue cooking until fork tender, about 2 hours. Remove from the oven and let rest for at least 30 minutes before slicing or shredding.
Meanwhile, make the rhubarb sauce:
Combine the rhubarb, sugar and water in a small saucepan set over medium heat. Bring to a boil, stirring often, and cook until the liquid thickens and the rhubarb is tender, 5-10 minutes. Remove from the heat and let cool slightly, then use an immersion blender to puree until smooth. Allow the sauce to cool completely. Serves 8-10