To make romesco: Preheat broiler. Cover sheet pan with parchment paper or foil. Place tomatoes on sheet pan and broil until well charred on both sides, 2-4 minutes per side. Transfer tomatoes to bowl; cool slightly then remove skin, core, seed and coarsely chop.

In blender, combine tomatoes; roasted red pepper; almonds; garlic; vinegar; paprika; red pepper flakes, if using; salt; and pepper until chunky paste forms. With blender on high speed, slowly drizzle in oil, scraping down sides of blender as needed until mixture creates rustic texture. Transfer romesco to bowl and taste for seasoning. Let romesco sit covered at room temperature 1 hour.

To prepare board: In bowl, drain tuna; set aside. Set grill on medium-high heat and brush grates with 1 teaspoon olive oil. Grill scallions until charred and tender, about 4 minutes per side. Remove to large plate and season with salt and pepper. Toss zucchini and red pepper in olive oil then season with salt and pepper. Grill until charred and tender, about 3 minutes per side. Remove to same plate to cool slightly.

To assemble: With large spoon, scoop generous amount of romesco into center of board. Using back of spoon, spread romesco into circle with well in center. Gently pile tuna into well. Arrange zucchini, pepper, roasted almonds, artichokes, radishes, olives and cheese around romesco and tuna. Sprinkle tuna with chopped parsley before serving.