In a saucepan on medium heat, mix sugar, red wine, water, cloves and zests of orange and lemon. Cook until sugar is dissolved and sauce thickens to syrup consistency. Add pears to saucepan and simmer 10-15 minutes until pears are heated through but not mushy. Remove pan from heat and stir in vanilla. Divide pears and syrup into individual dessert bowls, with syrup just barely covering the pears. Let pears cool in syrup for at least 20 minutes before serving. Serve with meringue or vanilla ice cream, if desired.