How to Make It
Place a rack in center of oven and preheat to 400°F. Cut garlic head in half horizontally and wrap each half in foil. Place on a rimmed baking sheet and roast until very soft, about 30 minutes. Carefully unwrap and squeeze out cloves into a blender or small food processor. Add oil, Parmesan, lemon juice, anchovies and 1/2 tsp. pepper. Blend until smooth.
Toss beans with romaine, 3 Tbsp. roasted garlic dressing, sun-dried tomatoes, parsley and 1/2 tsp. pepper. Divide among 4 plates and top with tuna. Drizzle with remaining dressing, sprinkle with additional pepper and serve.