Preheat oven to 350 degrees. Coat 9 x 13 pan with cooking spray and three tablespoons of flour, shaking gently to remove excess. In a large mixing bowl, combine 1 package lemon cake mix with 1 and 1/3 cups water, ¾ cup egg substitute, 3 T. poppy seed, and 1/3 cup unsweetened apple sauce. Beat on low for 30 seconds.
Scrape sides of bowl. Beat mixture on medium speed for two minutes. When done, split mixture into two portions, each 2½ cups. Pour one 2½ cups portion into 9 x 13 pan.
Clean mixing bowl. Combine 8 oz. package of softened cream cheese and ½ cup of powdered sugar. Mix on medium until mixture is smooth. Add can of lemon pie filling to mixture. Stir.
Using a teaspoon, distribute the cream cheese and lemon pie mixture across the top of the batter in pan. Gently spread throughout the pan.
Pour remaining batter on top, distributing evenly throughout pan.
In a small mixing bowl, combine 1/3 cup of brown sugar, 1/4 of chopped pecans, a half teaspoon of cinnamon. Mix. Add 3 tablespoons of flour. Mix again.
Add 4½ tablespoons melted butter and 1/8 teaspoon vanilla extract. Mix. Sprinkle mixture over batter in pan. Place pan into 350 degree oven for 40-45 minutes, or until a toothpick inserted into the middle comes out clean.
Remove pan from heat. Allow to cool completely. Blend ½ cup powdered sugar with 4 teaspoons lemon juice. Drizzle powdered sugar and lemon juice mixture over the top.
Store leftovers in refrigerator.