Walnut Romesco:
Place walnuts, tomatoes and garlic in food processor.
Pulse until finely chopped; add oil and pulse only until blended. Season with salt and pepper; set aside.
Salad Dressing:
Mix garlic with salt; add lemon juice, vinegar and mustard. Whisk in oil, add parsley.
Grill steaks to medium doneness. Let rest 15 minutes before sliced across the grain into thin diagonally sliced strips. For each serving, plate 3 cups mixed greens; top with approximately 100 g of steak.
Drizzle with 2 tbsp dressing. Garnish with 2 tbsp Walnut Romesco.