Preheat oven to 400 degrees. Sprinkle the grapes with half the sugar, and let stand 30 minutes. For the batter, in a bowl beat together the remaining sugar and egg yolks. Then beat in the egg. While beating, gradually add the butter, then the flour. Finally, add the rum flavoring, almond extract, and milk and beat until very smooth. May be done in the food processor.

Pour 1/3 of the batter into a heavily buttered 8- or 9-inch baking dish or pie pan. Spoon the grapes and their juice over the batter. Pour the remaining batter over the grapes. Bake the tart on the lower rack of the oven for 40 minutes, or until a toothpick comes out clean. The texture should be soft and nearly custardy. Cool slightly and serve from the pan in wedges or squares. May be done several days in advance. Serve warm, heated, or at room temperature. Yield: 4 to 6 servings