What to buy?
1/8 cups butter, softened
1/4 cups white sugar
1/4 teaspoons vanilla sugar
2 tablespoons grated lemon zest
1 tablespoon white sugar
1 teaspoon salt
5 eggs
2 cups all-purpose flour
1 teaspoon baking powder

How to make it?
1. Preheat the oven to 350 degrees F (175 degrees C). Grease and flour a 10 inch loaf pan.
2. Mix grated lemon rind with 1 tablespoon sugar.
3. Beat butter and sugar with vanilla sugar and lemon rind until the mixture becomes white and fluffy. Add eggs one at a time mixing after each one.
4. Mix flour and baking powder together and then carefully fold into the butter and egg mixture. Pour batter into prepared loaf pan.
5. Bake cake for 60 to 75 minutes or until a knife inserted in the middle comes out clean.

I got this recipe from allrecipes.com/Recipe/Botercake/Detail.aspx.
It's a delicious cooky!