Place the ranchera steak in a bowl and season with Street Taco seasoning, Chef Merito seasoning, garlic powder, and lemon juice. Toss to coat evenly and let it briefly marinate.
Preheat the Blackstone griddle to medium-high heat. Cook the steak until fully done and slightly charred, then chop into bite-sized pieces and set aside.
Add the corn tortillas to the griddle and cook until golden and crisp on both sides. Remove and let them cool so they finish crisping into tostadas.
For the guacamole, combine the jalapeño, onion, tomato, and cilantro in a bowl. Add the avocados and gently mash, leaving some texture. Stir in lemon juice, Knorr, salt, and pepper. Adjust seasoning to taste.
To assemble, spread each tostada with guacamole, then add chopped asada. Drizzle with sour cream, spoon on your favorite salsa, and finish with cotija cheese.
