In a bowl, combine the olive oil, minced garlic, cumin, chili powder, salt, black pepper, and lime juice. Add the flank steak and coat it well with the marinade. Cover and let it marinate for at least 30 minutes at room temperature or up to 4 hours in the refrigerator.
In another bowl, mix the masa harina, baking powder, and salt. Gradually add warm water, stirring until a soft and pliable dough forms. Divide the dough into golf ball-sized portions and flatten them into thick discs, about ½ inch thick.
Heat a griddle or cast-iron skillet over medium-high heat. Cook each gordita for about 3-4 minutes on each side until slightly charred and cooked through. Set aside and keep warm.
Preheat your grill or skillet over high heat. Remove the flank steak from the marinade and grill for about 4-5 minutes per side for medium-rare, or until desired doneness is achieved. Let the steak rest for 5 minutes before slicing it against the grain into thin strips.
Make a small slit in each gordita, creating a pocket. Stuff each gordita with slices of the carne asada. Top with chopped cilantro, diced onion, and salsa. Add avocado slices for extra creaminess.
Enjoy your carne asada gorditas warm, perhaps with an extra squeeze of lime over the top for zesty flavor.
Notes
Let the steak rest before slicing for better texture.