2Arrange plum halves, cut-side down, to cover the entire bottom of the pie plate. Sprinkle 2 tablespoons of sugar on top of plums.
3To make the custard: Combine remaining 3 tablespoons of sugar, eggs, milk, flour, lemon zest, cinnamon, vanilla, and salt in a blender. Process until smooth, about 2 minutes. Pour over arranged plums in the pan.