Bake cake and cool layers. Slice each layer in half to make 4 layers. Combine undrained pineapple, sugar, cornstarch and salt in a saucepan. Cook, stirring until clear and thickened. Remove from heat and stir in butter, lemon juice, and vanilla. Cool. Beat sour cream with electric mixer about 1 or 2 minutes. Spoon sour cream on each layer and then spoon pineapple filling on top of sour cream. End with top layer, sour cream and filling. Do not try to spread with knife as it will tear up the cake. Keep cake in refrigerator.