Blueberry Funny Cake-Pie

I pulled out the Farm Journal's Complete Pie Cookbook, c1965 and discovered that they have several blueberry pie recipes. I was a bit intrigued by this one:

Blueberry Funny Cake-Pie (With different sauces, I think this could be Strawberry, raspberry, etc.) (But not prunes)
Unbaked 1" pie shell
1/4 c. butter
3/4 c. sugar
1 egg
1 1/4 c. sifted cake flour
1 tsp. baking powder
1/2 tsp. salt
1/2 c. milk
1 tsp. vanilla
Blueberry Sauce
Vanilla
Cream butter; add sugar and mix thoroughly.  Add egg and mix well.  Sift flour with baking powder and salt; add alternately with milk to creamed mixture.  Add vanilla.
Pour batter into pie shell.  Gently pour lukewarm Blueberry Sauce over top.
Bake in moderate oven (375F) 35 - 40 minutes, or until cake tests done.  Serve warm with vanilla ice cream.  Makes 8 servings.

Blueberry Sauce:  Thoroughly drain 1 (15 oz.) can blueberries, saving 1 tblsp. juice.  Combine the 1 tblsp. juice with 1 tblsp. lemon juice, 1/2 c. sugar and blueberries.  Heat just until sugar is dissolved.  Cool to lukewarm.