Rub the skirt steak with the lime juice, oil, cumin and salt and let it stand for 15 minutes while a griddle heats over high heat.
Cook the steak for 3 to 5 minutes per side until browned and the thickest section reaches 145°F.
Rest the steak for 5 minutes, then slice it thinly across the grain.
Split the bolillos and toast the cut sides on the griddle for 1 to 2 minutes until crisp.
Spread the bottom halves with warm beans and the top halves with crema.
Layer the steak, Oaxaca cheese, avocado, tomato and pickled jalapeños over the beans.
Close each torta, press it gently and serve while the bread is crisp and the cheese has softened.