Make the Aji Verde: Add cilantro, jalapeños, mayonnaise, Parmesan, minced garlic, lime juice, and black pepper to a blender. Blend until smooth and creamy. Transfer to a bowl, cover, and refrigerate until ready to serve.
Prep Steak: Add sliced steak to a bowl. Drizzle with olive oil and toss. Add cornstarch, baking soda, smoked paprika, salt, cumin, oregano, and black pepper. Mix very well until evenly coated.
Cook Steak: Heat 2 tablespoons neutral oil in a large skillet or wok over high heat. Add steak in a single layer. Let it sear undisturbed for 1–2 minutes to develop deep color, then toss and cook until browned but not overcooked. Remove from the pan and set aside.
Cook Veggies: Add the remaining 1 tablespoon neutral oil to the same pan over high heat. Add red onion wedges and cook 2–3 minutes until slightly softened but still crisp with charred edges. Add minced garlic and cook about 30 seconds until fragrant.
Pour in beef broth and scrape up any browned bits from the bottom of the pan.
Add the tomato wedges and cook briefly, about 1 minute, just until they begin to soften but still hold their shape.
Return the steak to the pan.
Add soy sauce, aji amarillo paste, sugar, and distilled white vinegar directly to the pan. Toss everything together over high heat so the sauce coats the meat and reduces slightly.
Turn off the heat and fold in chopped cilantro. Gently fold in hot, crispy French fries so they absorb some sauce while keeping texture.
Serve immediately with warm white rice and aji verde on the side.