Combine first 3 ingredients in bowl. Add butter; rub with fingertips or cut in using pastry blender until mixture resembles coarse meal. Whisk yolks and 1 1/2 T water in small bowl to blend. Pour yolk mixture over flour mixture. Stir with fork to blend. Gather dough into ball; flatten into disk. Wrap in plastic and chill 1 hour.
Butter and flour 9-inch diameter tart pan with removeable bottom. Roll out dough on floured surface to 1/8-inch thick round. Transfer to part pan. Trim edges; reserve trimmings. Freeze crust until firm, about 30 minutes.
Preheat oven to 350°F.
Line crust with foil; fill with dry beans or pie weights. Bake until crust is set, about 12 minutes. Remove foil and beans. Bake crust until golden, about 12 minutes. Cool. Repair cracks in crust with reserved dough. Maintain oven temperature.
Using serrated knife, cut ends from lemons. Slice lemons into 1/8-inch thick rounds (or thinner). Remove any seeds.
Combine sugar, water and corn syrup in heavy large skillet. Stir over medium heat until sugar dissolves.
Place lemons in syrup; simmer 7 minutes. Turn top slices over; simmer until tender, occasionally pressing to submerge lemons in syrup, about 8 minutes longer. Cool 1 hour.
Line baking sheet with waxed paper. Using slotted spoon, transfer lemon slices to prepared sheet, arranging in single layer.
Boil syrup in skillet until reduced to 1 cup, about 3 minutes.
Cover lemons and syrup separately; chill until cold, at least 3 hours and up to 3 days.
Whisk all ingredients in medium bowl to blend. Pour into crust. Bake until filling is set, about 30 minutes. Cool completely. Chill until cold. (Can be made 8 hours ahead.).
Cut lemon slices in half; pat dry with paper towels. Arrange lemon slices in overlapping circles on filling. If lemon syrup is very thick, warm briefly over low heat. Brush lemons with enough syrup to glaze.