How to Make It
Preheat the oven to 325°. Season with brisket with salt and cracked black pepper. Heat the canola oil in a large enameled cast-iron casserole. Add the brisket and cook over moderately high heat until browned all over. Transfer the brisket to a plate.
To the casserole, add the onion, carrots, celery and garlic and cook over moderately low heat, stirring occasionally, until softened, about 5 minutes. Stir in the tomato puree, chipotle, thyme, cumin, oregano and bay leaf and cook for about 5 minutes, stirring occasionally.
Add the brisket to the casserole along with enough water to cover it. Bring to a boil, then lower the heat to a simmer. Cover the casserole with foil and transfer to the oven. Braise for 2 to 3 hours, until the meat is tender. Remove the casserole from the oven and let the brisket cool completely in the braising liquid.
Remove the brisket from the liquid and thinly slice it. Discard the bar leaf and thyme sprigs from the liquid and discard. Pout the braising liquid into a blender or food processor and blend until smooth. Add the sauce back to the casserole and bring to a simmer. Return the meat to the pot to rewarm it. Season with salt and pepper.
In a medium bowl, using your hands, mix the matzo meal and salt with the water and olive oil until a soft dough forms. Form the dough into 1 1/2-inch balls. Lay each ball between 2 sheets of plastic wrap and roll or press until a tortilla forms.
Heat a nonstick skillet over moderate heat. Cook the tortillas on each side until golden and cooked through. Serve the tortillas with the braised brisket, topped with red onion and avocado.