In a mixing bowl, combine the flour, sugar and salt. Mix well. Add the shortening and mix until the mixture resembles coarse crumbs. Add the water and let sit 1 minute. Either using a fork or your hands, carefully press the mixture together to form a soft ball. Wrap in plastic wrap and refrigerate at least 30 minutes.
In the top of a double boiler over simmering water, cook the sugar, lemon juice, butter, zest and eggs, whisking frequently, until a custard forms and bubbles appear on surface, 10 to 15 minutes.
Line the tart pan with parchment paper and weight with pie weights or beans and place in a 350ºF oven for 15 minutes, or until golden brown and cool completely.
Remove the lemon curd from the heat and strain through a fine mesh sieve into a bowl.
Spoon the lemon curd into the prepared tart shell, smoothing the top with the back of a spoon or rubber spatula.
Arrange the berries in a decorative pattern over the top.
Serve with whipped cream on the side, if desired.
Yield: 6 - 8 servings