In a bowl, combine 1 cup yogurt, 1 1/4 teaspoons salt, pepper, fish sauce, lime juice, lime zest, vinegar, chili paste, dill weed and honey. Add Steak and let marinade for 15 minutes. Drain well and reserve liquid.
Preheat oven to 400°. Place steak on a broil pan and place in the oven. reduce the heat to 350°after placing the steak in the oven. This will quickly seal the meat to retain the moisture. Cook for 5-7 minutes.
In a medium skillet, over medium heat, add olive oil and saute onions until translucent. Add reserved marinade; reduce heat to medium and cook for 5 minutes. Remove from heat. Stir in 2 cups of yogurt. Add cooked skirt steak. Return to heat and warm if necessary.
Divide watercress between 6 plates. Arrange steak on top of watercress. Garnish each with a dollop of remaining yogurt.