Preheat the oven to 350 F. Line an 8x8 inch pan with parchment, leaving an overhang on two sides.
Mix the flour, powdered sugar and salt, then work in the cold butter with your fingertips until crumbly. Press evenly into the pan.
Bake the crust for 18 to 20 minutes, until lightly golden.
Whisk the condensed milk, heavy cream, cornstarch, lemon zest and turmeric until smooth, then whisk in the lemon juice until slightly thickened.
Pour the filling over the warm crust and bake for 16 to 18 minutes, until the edges are set and the center barely jiggles.
Cool at room temperature for 1 hour.
Refrigerate for at least 3 hours, until fully firm.
Lift out using the parchment, dust with powdered sugar and cut into squares, wiping the cutter clean between cuts.
