Step 1Using tongs, hold the bell peppers directly over a gas flame, turning until all sides are blackened, 6 to 8 minutes. Place the peppers in a bowl and cover them with plastic wrap to steam, about 10 minutes. Remove the charred skins and seeds. Set the peppers aside.
Step 2Combine the oil, almonds and garlic in a small pan and heat gently over medium heat until the almonds begin to color; turn off the heat and retrieve the almonds and garlic promptly with a slotted spoon. Reserve the oil.
Step 3Grind the almonds, garlic and peppers to a paste in a mortar or blender and slowly add the oil. Season with the salt, cayenne and vinegar. Serve at room temperature.
Step 1Measure the thickness of the fish and calculate 10 minutes per inch; keep track of this number. Insert a thin wooden skewer into the fish and feel the resistance as you cut your way into the meat and the grip as you try to remove it. This is part of the "skewer test" which will help you determine when the fish is done. Season the fish with a little salt and pepper, then marinate with the oil, a few herb sprigs and the lemon juice for up to 2 hours in the refrigerator; remove from the refrigerator 30 minutes before cooking.
Step 2Heat an outdoor or stove-top grill over medium-high heat, or heat the broiler with a rack set so the fish will cook about 3 inches from the heat.
Step 3Grill or broil the fish slightly more than half the estimated time above, then turn once and continue cooking until the fish is done by the skewer test. In a fully cooked piece of fish, the skewer will slide in and out with almost no resistance. The trick is to use it as a probe to catch that point where there is still a little resistance in the center. If it's 90% done, figure the fish will cook the remaining 10% after it comes off the fire, as the heat from the surface equalizes with the center. Serve immediately on warm plates, with a dollop of Romesco Sauce alongside.