Preheat oven to 350 degrees
Grease shallow baking dish (9x13) with cooking spray or butter & dust with 1 tbsp granulated sugar - set aside
Prepare plums & place in a medium bowl
Add lemon juice, 1 tbsp sugar to plums & toss to coat
In a blender, combine vanilla, eggs, milk, flour, salt, half & half, remaining 1/2 cup sugar & blend on high until frothy (1 minute)
Transfer plum mix into bottom of prepared baking dish
Pour blender mixture on top - no need to stir
Bake until just set - 45-50 minutes
Let cool 15 minutes
Dust with confectioners sugar & serve with vanilla ice cream or whipped cream if desired