In bowl, stir together flour, sugar and salt. Cube butter; using pastry blender, cut into flour mixture until crumbly. Using hands, press mixture into small handfuls until smooth and dough holds together. Press evenly into bottom and up side of 25 cm flan pan with removable bottom. Using fork, prick crust at 3 cm intervals. Bake in 350 degree oven for about 20 minutes or until light sandy colour. Let cool on rack.
Filling: In saucepan, stir together sugar, cornstarch and salt. Whisk in one third cup cold water, 2 cups of the blueberries and lemon rind. Bring to simmer over medium heat; reduce heat and simmer gently, stirring often, for about 10 minutes or until mixture is glossy and thick. Remove from heat. Stir in lemon juice and butter. Let cool slightly. Gently stir remaining berries into saucepan. Spoon mixture into prepared crust; smooth top. Refrigerate for about 30 minutes or until set.
Pie can be made ahead and refrigerated for up to 8 hours.
Topping: spoon yogurt into paper towel-lined sieve set over bowl. Let drain in refrigerator for 4 hours or until yogurt measures 0.75 cup. Whip cream; stir one-quarter into yogurt. Fold in remaining cream. Spoon over berries.