For crust, stir together piecrust mix and yogurt in a medium mixing bowl until moistened. Form dough into a ball. Divide into 36 equal portions. Form each portion into a ball. Place each ball in an ungreased 1-3/4-inch muffin cup. Press dough evenly against the bottoms and up the sides of cups. Cover and set aside.
For filling, stir together eggs, sugar, butter or margarine, milk, cornmeal, lemon peel, and lemon juice in a small mixing bowl. Fill each pastry-lined cup with about 2 teaspoons of the filling.
Bake in a 350 degree F oven for 25 to 30 minutes or until lightly browned and set in centers. Cool slightly in pans. Carefully remove tarts from pans and cool on wire racks.
To serve, if desired, garnish with red and green candied cherries or spoon 1/2 teaspoon jelly into the center of each tart. Makes 36.