Prepare the aji sauce. Blend romaine - garlic until smooth. Set aside.
Preheat frying oil to 350 degrees.
Fry french fries until golden and crispy. Drain on paper towels and set aside.
Heat oil in a large saute pan over medium-high heat. Add the tri-tip and season with salt and pepper. Saute until browned on both sides. Remove from heat and set aside.
Add the onions in the same pan and saute until softened, about 3 minutes. Add the tomatoes and cook until softened, about 1 minute. Return the beef to the pan with the french fries, vinegar, and soy sauce. Toss to combine and continue to cook until beef is no longer pink. Season with salt and pepper and sprinkle with chopped parsley. Serve.