Melt In Your Mouth Blueberry Cake
["1 1/2 c. flour", "1 tsp. baking powder", "1/2 tsp. salt", "1/2 c. shortening", "1 c. sugar", "2 egg yolks", "1 tsp. vanilla", "1/3 c. blueberries"]
["Grease and flour an 8-inch square pan.", "Heat oven to 350\u00b0."]
["flour", "baking powder", "salt", "shortening", "sugar", "egg yolks", "vanilla", "blueberries"]