• Crisp up the corn tortillas by preheating the oven to 400°, spraying both sides of the tortillas with cooking spray, and placing them on a rimmed baking pan.
• Bake for approximately 10 minutes, until crispy.
• Prepare the potatoes by washing them thoroughly and dicing into bite-sized pieces.
• Place the diced potatoes into a bowl and drizzle with two tablespoons of olive oil.
• Add the cumin, salt and pepper, and mix well.
• Place the seasoned potatoes into a grill basket and grill for approximately 35 minutes on high heat until golden brown and fork tender.
• Season the beef tenderloin with steak seasoning, place on the grill and cook to medium-well.
• Remove from grill, cover loosely with a tent of aluminum foil and allow to rest for 10 minutes prior to slicing into thin pieces.
• Prepare the chimichurri sauce by combining all ingredients for the sauce together in a medium-sized bowl and mixing well.

Assembly

• To assemble the grilled steak and potato tostadas, place a crispy corn tortilla onto a plate. Pile 1/2 cup of the grilled potatoes onto the tortilla place three to four slices of the grilled steak over the potatoes.
• On top of the steak add a large pinch of shredded spinach, a few slices of tomato and some slivers of onion.
• Drizzle on about a tablespoon or so of the chimichurri sauce and serve.