Preheat oven to 400 °F (205 °C).
Butter or line large muffin pan cups with paper cups.
In a bowl, beat egg.
Mix in milk, margarine and lemon peel.
In a second bowl, mix flour, baking powder, salt and sugar.
Fold in liquid mixture, stirring only as needed to moisten dry ingredients.
In a third bowl, mix cream cheese, icing sugar and lemon juice until creamy.
Half fill muffin cups with first mixture.
Spoon 1 tsp (5 mL) cheese mixture in the center of each muffin.
Fill muffin cups with remaining batter.
Bake in oven 20 minutes.