How to Make It
Preheat oven to 375°F. Butter a 2 1/2-quart, 9-inch square baking dish. Sprinkle blueberries evenly over bottom.
Whisk together flour, sugar, and salt in a large bowl. Whisk in cream, eggs, melted butter, and vanilla until completely smooth. Let batter stand 5 minutes. Slowly pour batter evenly over blueberries.
Bake in preheated oven until clafoutis is golden brown and set in center, 25 to 30 minutes. Let stand 10 minutes. Sprinkle with powdered sugar just before serving.