Trim artichokes stems to 1/2 inch. Place upright in large kettle and add enough water to cover. Add lemon juice, 1 tablespoon salt, pepper, oregano and red pepper flakes. Bring to boil, reduce heat and simmer about 1 hour or until leaves pull easily from base of artichokes. Remove from pan and invert artichokes to drain thoroughly and cool. Using spoon, remove chokes and discard. To make vinaigrette, combine oil, vinegar, garlic, oregano, red pepper flakes, capers and pimiento in medium bowl. Season to taste with salt and pepper. Blend well. Stand artichokes upright in serving dish.