Cut the pears into halves and remove the cores. Place, cut side down, in aglass baking dish that contains the lemon juice and wine.
Bake, covered, for about twenty minutes, or until the pears are beginning to soften.
Turn the pears and sprinkle with the sugar. Fill with grapes. Return to the oven and cook, uncovered, until tender and glazed. Pour the cognac over the pears and serve warm or chilled. If desired, flame the cognac before pouring it over the pears.