01 -
In a bowl, stir together the olive oil, lime juice, minced garlic, ground cumin, smoked paprika, salt, and black pepper until smooth.
02 -
Put the steak in a zip-top bag or a shallow dish. Pour the marinade all over it, seal the bag or cover the dish, and pop it in the fridge for at least an hour, though overnight works even better.
03 -
Heat up a grill or a cast-iron skillet over high heat. Take the steak out of the marinade (let the extra liquid drip off), and cook it for 5–7 minutes per side or till it’s as done as you like. Give it a rest, then cut thin slices against the grain.
04 -
Lay out the tostada shells. Pile on the sliced steak, spread some guacamole, plop on sour cream or crema, and finish with chopped tomatoes, cilantro, and maybe jalapeños if you like it spicy.
05 -
Serve right away with lime wedges on the side for a little squeeze of flavor.