- 1
**Braise the tongue:** Place the beef tongue in a large pot with the quartered onion, garlic, bay leaves, peppercorns, oregano, and enough water to cover by 2 inches. Bring to a boil, skim the foam, then reduce heat to a gentle simmer. Cover and cook for 2.5–3 hours, until the tongue pierces easily with a fork.
- 2
**Peel and cube:** Remove the tongue and let it cool enough to handle. Peel and discard the tough outer skin while it's still warm — it slips off easily. Trim any fatty or gristly base portions. Cut the meat into 3/4-inch cubes. (You can braise the tongue a day ahead and refrigerate.)
- 3
**Make the tomatillo salsa:** Broil or char tomatillos, serranos, garlic, and onion in a dry skillet or under the broiler until softened and lightly blackened, about 8–10 minutes. Blend with cilantro and salt until smooth but slightly textured. Taste and adjust seasoning.
- 4
**Quick-pickle the red onion:** Combine sliced red onion with apple cider vinegar, sugar, and a pinch of salt. Let sit at room temperature for at least 30 minutes while you prepare everything else.
- 5
**Sear the lengua:** Heat a cast-iron skillet or heavy pan over high heat with a thin film of neutral oil. Add the cubed tongue in a single layer (work in batches if needed) and sear without moving for 1–2 minutes until a golden crust forms. Toss and sear another minute. Season with salt.
- 6
**Warm the tortilla:** Heat the flour tortilla directly over a gas burner or in a dry skillet for 20–30 seconds per side until warm, pliable, and slightly charred in spots.
- 7
**Build the burrito:** Lay the warm tortilla flat. Spread a band of warm refried beans across the lower third. Add rice, then a spoonful of tomatillo salsa, then the seared lengua. Top with crema, pickled red onion, and cilantro.
- 8
**Roll tightly:** Fold the sides in first, then roll from the bottom up, keeping firm pressure on the filling as you roll. Place seam-side down.
- 9
**Toast the exterior (optional but recommended):** Return the rolled burrito to the hot dry skillet, seam-side down for 30 seconds, then flip to toast the top. This seals the burrito and adds a satisfying crust.
- 10
**Serve** sliced diagonally with extra salsa verde and lime wedges on the side.