Allow steaks to rest at room temperature to take the chill off of them. Pat the steaks with paper towels to remove any juices. Preheat cast-iron skillet or griddle over medium-high heat.
Place ancho and stock in a small pot, bring to boil then simmer a few minutes over low heat to soften the pepper. Purée softened pepper and stock in food processor, return to pot and combine with tomato sauce, salt and pepper.
Meanwhile, mix the juice of lime or lemon with garlic paste. Add the finely diced avocado, tomato, pepper, red onion and herb of choice to the bowl; season with a healthy pinch of salt and gently combine with fingertips or fork.