Combine the dry spices for seasoning the meat. Add salt to taste. Season the meat on both sides and set aside.
While the beef marinates a bit, preheat a skillet to medium heat. Add 2 tablespoons of olive oil. Add the onions and chile serrano. Season lightly with salt and pepper. Saute for 8 to 10 minutes, stirring as needed. Transfer to a bowl and set aside.
In a bowl, combine all of the ingredients for the roasted garlic crema. Taste for salt and set aside. In the skillet you cooked the onions, add 2 more tablespoons of olive oil and preheat at medium for 3 to 4 minutes or until skillet is hot.
Sear and brown the seasoned beef for 2 1/2 to 3 minutes per side. Transfer to cutting board and slice thin or chop. Place back into skillet at medium heat. Mix in the cooked onions and chile pepper mixture. Add the juice of 1/2 a lime and mix to combine. Serve on warm, thick flour tortillas. Garnish with toasted chile de arbol salsa, lime and chopped cilantro. Yields 4-5 servings.