Place grapefruit topped with brown sugar under the oven broiler for approximately 5 minutes. Sauté pear strips over medium heat in tablespoon butter and sprinkle 1 tablespoon brown sugar into pan and gently stir in, cooking for about 4-5 minutes until pears are caramelized.
Assemble lettuce, onions and spinach together in a large bowl. Scatter grapefruit pieces, allowing grapefruit juices to drip into the salad, and pears on top. Sprinkle pomegranate seeds over the entire salad. Dress salad with the chilled Pear/Lemongrass Vinaigrette.
Whisk all ingredients together and refrigerate until ready to use.