Place the steak pieces into a ziploc bag. Add the marinade ingredients to the bag and move the steak around until it's all coated. Keep in the fridge until ready to grill.
Make the spanish rice (homemade or just make up a box of Rice Roni Spanish Rice. Dice the tomatoes and slice the lettuce.
For the dressing, mix together the ranch dressing and the salsa verde until combined.
When ready to prepare, heat a grill to high heat. Place the pieces of steak on the grill and sear on high heat the bottom side of each of the steaks. After 3-5 minutes, turn the steak over to the other side and continue to grill until the center of the steak is your desired doneness level (rare, medium rare, well done, etc.). This cooking time will vary depending on the size and thickenss of your steak.
When the steak is cooked to your liking, remove from the grill and let rest on a plate for 5 minutes. After it's rested, slice the steak into thin strips and set aside.
To prepare the tostadas, place a tostade on the bottom of a plate. Add on top the Spanish rice, some lettuce, cheese, the grilled steak, diced tomatoes, cilantro (optional garnish). Drizzle the ranch dressing on the top and serve.