Combine blueberries, 1/4 cup of the sugar and lemon rind in a buttered 8 inch square baking pan.
In a bowl, combine flour, baking powder and salt.
In another bowl, cream shortening with remaining 1/2 cup sugar until fluffy. Beat in egg and vanilla. Add dry ingredients alternately with milk, blending well after each addition and finishing with dry ingredients.
Pour batter over fruit and bake in a preheated 350°F oven for about 40 minutes, or until a toothpick inserted in centre comes out clean.
Let cool slightly; turn out onto serving plate. Cut in squares and serve at room temperature. Top this off with whipped or ice cream, if desired.