Preheat oven to 350°F. Butter 8x8x2-inch glass baking dish. Blend buttermilk, 1/2 cup sugar, egg yolks, lemon juice, flour, butter, and salt in blender until smooth. Transfer buttermilk mixture to medium bowl. Using electric mixer, beat egg whites in large bowl until soft peaks form. Gradually add remaining 1/2 cup sugar and beat until stiff but not dry. Gently fold buttermilk mixture into whites in 3 additions (batter will be runny).
Pour batter into prepared dish. Place dish in roasting pan. Pour enough hot water into roasting pan to come halfway up sides of dish. Bake until entire top is evenly browned and cake moves very slightly in center but feels slightly springy to touch, about 45 minutes. Remove dish from roasting pan.
Cool cake completely in baking dish on rack. Refrigerate until cold, at least 3 hours and up to 6 hours. Spoon pudding cake out into shallow bowls. Pour cream around cake. Top with berries.
Recipe courtesy of epicurious.com