Process raspberries with syrup in blender or food processor until smooth. Strain through sieve into small bowl. Discard seeds.
Combine cornstarch and sugar in medium saucepan. Stir in lemon juice and raspberry puree until smooth. Heat and stir on medium for about 5 minutes until boiling and thickened. Remove from heat.
Reduce heat to medium low. Add eggs yolks, butter and lemon zest while stirring constantly. Heat and stir for about 1 minute until butter is melted. Remove from heat. Makes 3 1/4 cups (800 mL) filling.
Beat egg whites in medium bowl until soft peaks form. Add sugar, 1 tbsp (15 mL) at a time while beating, until stiff peaks form and sugar is dissolved.
Pour raspberry filling into pie shell. Spread evenly. Spoon meringue topping over filling. Spread evenly to edge of pastry. Swirl meringue to create decorative peaks. Bake in 350 F (175 C) oven for 10 to 12 minutes until meringue is golden. Let stand for at least 3 hours before serving.