In a large bowl, toss apples with lemon juice and vanilla. Combine the pecans, sugars, cinnamon and cornstarch; add to apple mixture and toss to coat. Pour caramel topping over bottom of pastry shell; top with apple mixture (shell will be full). Drizzle with butter.
In a small bowl, combine the flour, pecans and sugar. Cut in butter until mixture resembles coarse crumbs. Sprinkle over filling.
Bake at 350° for 55-65 minutes or until filling is bubbly and topping is browned. Immediately drizzle with caramel topping. Cool on a wire rack. Yield: 8 servings.
Nutrition Facts: 1 piece equals 608 calories, 35 g fat (12 g saturated fat), 39 mg cholesterol, 267 mg sodium, 74 g carbohydrate, 6 g fiber, 5 g protein.