Heat oven to 350°F. Grease and flour bottom and sides of 9 or 10-inch springform pan. In large bowl, combine 2/3 cup sugar and margarine; beat until light and fluffy. Add lemon peel and egg; beat 2 minutes at medium speed.
Lightly spoon flour into measuring cup; level off. In medium bowl, combine 1 1/2 cups flour, poppy seed, baking soda and salt; mix well. Add to margarine mixture alternately with sour cream, beating until well combined. Spread batter over bottom and 1 inch up sides of greased and floured pan, making sure batter on sides is 1/4 inch thick.
In another medium bowl, combine all filling ingredients; mix well. Spoon over batter.
Bake at 350°F. for 45 to 55 minutes or until crust is golden brown. Cool 10 minutes; remove sides of pan.
In small bowl, blend powdered sugar and enough milk for desired drizzling consistency. Drizzle over warm cake. Serve warm or cool.