1½tablespoonsred wine vinegar or sherry vinegar, or more to taste
Fresh lemon juice
Salt and freshly ground black pepper, to taste
pinch of cayenne
3tablespoons chopped fresh herbs, such as parsley and chives
To make the Romescu Sauce: Heat the broiler, with a rack set so the bell peppers can fit under the heat source (Bell Pepper Basics). Place a large sheet of foil on a baking sheet and arrange the peppers and garlic on it; rub lightly with a little olive oil. Broil, turning frequently with tongs, until the peppers and garlic are evenly charred. The garlic usually takes 8 to 10 minutes; remove when it is done. The peppers usually take 12 to 15 minutes; remove from the broiler with tongs, slip into a paper bag, and close. Let stand until cool enough to handle.
Meanwhile, toast the almonds and hazelnuts in a dry skillet over medium heat, stirring frequently, until fragrant and beginning to become lightly golden, usually about 8 minutes. Remove from the heat and set aside to cool.
Cut the bell peppers in half. Working over a bowl to catch the juices, remove the charred skins, seeds, and stems from the peppers. Coarsely chop the flesh. Strain the pepper juices and reserve. Trim off the hard stem ends from the roasted garlic and peel off the skins. Place the bell peppers, garlic, almonds, hazelnuts, and tomatoes in a food processor or blender; process until nearly smooth. With the machine running, gradually add ⅓ cup olive oil in a thin stream. Blend in the vinegar, a squeeze of lemon juice, salt and black pepper, and the cayenne. Scrape the sauce into a small bowl; stir in the herbs. Now taste and correct all seasonings if needed, adding more salt, pepper, cayenne, vinegar, and lemon juice; this sauce should be well seasoned, with a slight tang of vinegar. Cover and set aside at room temperature for at least 30 minutes. Taste and correct the seasonings again before serving. (The romescu sauce can be made a few days ahead and refrigerated, tightly covered.)
To make the Beer-Steamed Shrimp (Steaming Basics): Bring the beer and Crab Boil (or spices) to a boil in the bottom of a steamer. Arrange the shrimp over a steamer rack, tightly cover, and steam just until the shrimp turn pink, 3 to 4 minutes. Quickly stir the shrimp once about halfway through the cooking time. To serve hot, just arrange the shrimp on a platter as described below in step 5 and dig in. To serve cold, place the shrimp in a single layer in a large bowl or shallow pan of ice. When cold, drain well on paper towels and arrange on the platter.
To serve, select a narrow serving bowl and scrape the romescu sauce into the bowl. Place the bowl in the center of a large serving platter. Arrange the shrimp around the bowl, scatter with lemon wedges, and serve hot or cold.