In large glass or metal bowl using electric mixer, beat egg whites with cream of tartar, vanilla and salt until foamy. Gradually add 3/4 cup of the sugar, beating constantly, until mixture holds stiff peaks.
In separate bowl, mix together flour and remaining sugar. Gently fold flour mixture, one quarter at a time, into egg whites. Spoon batter into un-buttered 10 inch tube pan with removable bottom; smooth top.
Bake in 350°F oven for 40 minutes or until cake springs back when lightly touched. Turn pan upside down (if it doesn’t have feet, balance edges on two cans); let cool completely.
Prepare lemon pie filling according to package instructions, but use ONLY 1 1/4 cups water per package. Press plastic wrap onto surface of pie filling; let cool to room temperature. Whip cream until very thick. Stir a large spoonful of cream into pie filling to lighten it. Fold in remaining cream.
Using serrated knife, cut cake horizontally into three equal layers. Spread some lemon cream over first layer; top with 1/2 cup of the blueberries; top with next cake layer. Repeat. Spread remaining lemon cream mixture thickly all over cake. Top with remaining blueberries. Store in refrigerator. Makes 12 servings.