Sift together the flour, baking powder, salt and ¾ cup sugar. Add shortening, milk, vanilla and ½ tsp. grated lemon peel. Beat with an electric mixer on medium speed for 3 minutes, or 300 strokes by hand.
Add the egg and beat with the mixer 2 minutes longer (200 strokes by hand).
Turn into a greased 8" square pan.
Lightly stir together the blueberries, 3 tbsp. sugar and 1 tsp. grated lemon peel. Sprinkle over the batter in the pan.
Bake in a moderate oven (350°) for 40 to 45 minutes, or until lightly browned. Cool slightly in pan. Cut in squares and serve warm.