Preheat oven to 400 degrees. Butter a 1-quart baking dish (not metal) using a pastry brush; sprinkle 2 tablespoons granulated sugar over bottom. Sift remaining 1/2 cup granulated sugar, the flour, and salt into a large bowl. Gradually whisk in eggs, 3/4 cup cream, the milk, and zest.
Scatter cranberries into dish; pour batter over top. Bake until puffed, slightly set, and brown around edges, 32 to 34 minutes. Let cool on a wire rack for 15 minutes (it will sink).
Whisk remaining 1/4 cup cream until soft peaks form. Dust clafouti with confectioners' sugar. Serve with whipped cream.