SWEET PASTRY: In large bowl, stir together flour, sugar, orange rind and salt. With pastry blender or 2 knives, cut in butter until crumbly.
Whisk together eggs, water and lemon juice; drizzle over flour mixture, tossing with fork until moist enough to shape into ball (dough will be slightly sticky). Flatten into disc; wrap and refrigerate for 30 minutes or up to 3 days. Let soften to room temperature before rolling.
On generously floured pastry cloth and using stockinette-covered rolling pin, roll out half of the pastry at a time to 1/8 inch thickness. Cut into 3 1/2 inch rounds; ease into shallow 2 3/4 inch tart shells. Refrigerate for 30 minutes.
Line each tart shell with foil; fill with pie weights or dry beans. Bake in 400°F oven for about 10 minutes or until light golden and firm. Remove foil and weights; let cool.
FILLING: In bowl, combine sugar, flour and orange rind; blend in sour cream and egg yolk. Spoon about 1 tablespoons berries (mossberries or wild blueberries) into each tart shell; cover with about 1 tablespoons filling and top with 3 or 4 berries. Bake in 350°F oven for about 20 minutes or until pastry is golden and filling is set. Let stand for 1 minute. Remove from pan and let cool on racks. Makes about 24 tarts.