Cream the butter at medium speed in the bowl of an electric mixer. Slowly add the sugar and lemon zest to the butter, and keep creaming at medium speed for one minute, until the mixture is light in color and fluffy.
To make this cake into an 8” cake, use 2-8” cake pans, but you won’t be able to have 2 layers of Blackberry Jam filling, only one of the jam filling, and one filled with the Lemon Curd. To make 3-8” layers, make 1.5 recipes of the cake, by simply multiplying each measurement by 1.5. Time baking will vary, and might take longer to bake the 8” cakes. Check for doneness by reading the tips above.