For Filling: In a large saucepan, blend sugar and cornstarch together; stir in prepared fruit and lemon juice. Cook over medium heat, stirring constantly, until thickened. Pour into a 9x13 pan. Top with cake batter.
For Cake: In a large bowl, combine all ingredients and mix just until blended, and flour is absorbed. Pour evenly over fruit in 9x13 pan. Bake at 375º F. for 30-40 minutes, or until filling is bubbly and top is golden brown. Serve warm with whipping cream or ice cream.