- Heat oven to 450°F. Bake pie crust as directed on box for One-Crust Baked Shell, using 9-inch tart pan with removable bottom or 9-inch glass pie plate. Cool on cooling rack 15 minutes.
- In 2-quart saucepan, mix sugar, cornstarch and flour. Gradually stir in water, stirring until smooth. Heat to boiling over medium heat; cook and stir 1 minute longer. Remove from heat. Quickly stir about 1/2 cup hot mixture into beaten egg yolks; mix well. Gradually stir egg mixture back into hot mixture. Stir in lemon peel and lemon juice. Cook over medium heat about 5 minutes, stirring constantly. Remove from heat. Add butter; stir until melted. Let stand 10 minutes.
- Carefully pour hot lemon filling in crust. Cool 2 hours; top with blackberries ans strawberry slices. Refrigerate until serving time. Remove side of pan. Cover and refrigerate any remaining tart.