for the tart shell
2 1/2 cups all purpose flour
1 tablespoon sugar
3/4 teaspoon salt
10 tablespoons (1 1/4 sticks) chilled unsalted butter, cut into 1/2-inch pieces
1/3 cup chilled solid vegetable shortening, diced
6 tablespoons (or more) ice water
for the filling
4 large eggs
1 1/2 cups sugar
1 cup fresh lemon juice (about 5 lemons)
1/4 cup heavy cream
1 lemon, zested
Pinch kosher salt
1 1/2 pints blueberries
Blend flour, sugar and salt in processor. Add butter and shortening and cut in using on/off turns until mixture resembles coarse meal. Add 6 tablespoons ice water and process until moist clumps form, adding more water by teaspoonfuls if dough is dry. Gather into ball and then flatten into a disk. Wrap in plastic and chill for a couple of hours.
Preheat oven to 350F.
Roll the dough out on a lightly floured surface into a 12-inch circle. Roll the dough up onto the pin and lay it inside a 10-inch tart pan with a removable bottom. Press the dough into the edges of the pan and fold the excess dough
inside to reinforce the rim. Cover the tart pan with plastic wrap and put it into the refrigerator for another 30 minutes to rest.
Put the tart pan on a baking sheet and prick the bottom of the dough with a fork. Cover the shell with a piece of parchment paper and fill it with pie weights or dry beans. Bake for 25 minutes. Remove the parchment and weights and set aside to cool.
Whisk together the eggs, sugar, lemon juice, cream, zest, and salt. Pour filling into cooled tart shell and bake for 20 to 25 minutes. Let cool completely again before arranging the blueberries on top of the lemon filling. Serve at room temperature.