Grease and generously flour (or line with wax paper) two 9x9-inch layer pans or 9x13-inch oblong pan.
Sift together flour, sugar, baking powder and salt. Cut in shortening. Pour in half of the milk, also add lemon extract and vanilla. Blend. Add remaining milk; beat 2 minutes. Add egg yolks. Mix well. Pour into prepared pans.
Bake at 350 degrees until cake tests done, 25 to 35 minutes for layers and 40 to 50 minutes for square or oblong. Cool and finish with desired frosting.
For smaller cake: 1 3/4 Cup Flour, 1 1/4 cup Sugar, 3 Teaspoons Baking Powder, 3/4 Teaspoon Salt, 3/8 Cup Shortening, 1 Cup Milk, 3/4 Teaspoon Lemon Extract, 1/4 Teaspoon Vanilla, 4 Egg Yolks.