Steak Torta with Charred Onions, Melted Cheese and Pickled Jalapeños - Rick Bayless

Ingredients

• About 2/3 cup cooked beans (any color is welcome here) with enough liquid to cover, canned or home-cooked
• 1 or 2 tablespoons fresh-rendered pork lard or bacon drippings or vegetable oil
• Salt
• 1 pound (about ½ of a medium) flank steak
• OR 1 pound outside skirt steak, trimmed of most surface fat
• 1 large (8 ounce) onion, sliced into ¼-inch rounds
• Oil for spraying or brushing
• Fresh black pepper
• 4 bolillos
• 8 slices (4 to 6 ounces) Chihuahua or Mexican Manchego cheese (or other melting cheese like Jack, Colby or mild cheddar)
• 4 large pickled jalapeños, stemmed, seeded and thinly sliced lengthwise
• About ¾ cup Roasted Tomatillo Salsa (optional)