Combine raisins and whiskey in small bowl; set aside to soak. Cook onion in oil in a large skillet over medium-low heat until tender and golden brown, about 15 minutes, stirring occasionally. Stir in brown sugar and continue to cook 5 minutes. Stir in tomatoes, raisins and whiskey. Bring to a boil. Reduce heat and simmer 10 minutes or until thickened. Season with thyme, salt and pepper. Cool, cover and refrigerate. Serve chilled or at room temperature.