1. Beat butter with sugar until creamy.
2. Add eggs one at a time, beating until well blended.
3. Add flour, baking powder, and lemon rind, beat 4 minutes.
4. Pour into greased 9-inch spring-form pan.
5. Arrange the apples on the batter, sprinkle with 2 teaspoons sugar.
6. Bake 1 hour at 350 degrees.
7. Remove from pan, brush apples with jam, cool.