This is the best recipe for a Pudding Cake of a few which I tested by different chefs.
I got it from the American Test Kitchen while watching episode: The Chemistry of Cakes.
Originally it was a Lemon Pudding Cake. The addition of raspberries and orange is my idea.
This dessert is best served warm or at room temperature the same day it is made.
Adjust oven rack to lowest position and heat oven to 325 degrees. Grease 8-inch square baking dish.
Whisk flour and cornstarch in a mixing bowl.
With an electric mixer on medium-high speed, beat 1/2 cup sugar, butter, and orange zest until light and fluffy, about 2 minutes.
Beat in yolks, one at a time, until incorporated. Reduce speed to medium-low. Add flour and cornstarch mixture, and beat until incorporated. Slowly add milk and orange juice, gently mixing until just combined. With a rubber spatula fold in the raspberries.
In a clean bowl beat egg whites on medium-high speed until soft peaks form, about 2 minutes; then slowly add remaining sugar until whites are firm and glossy, about 1 minute. Whisk one-third of whites into batter, and then gently fold in remaining whites, one scoop at a time, until well combined.
Place kitchen towel in bottom of roasting pan and arrange prepared baking dish on towel. Spoon batter into prepared dish. Carefully place pan on oven rack and pour boiling water into pan until water comes halfway up the sides of baking dish.
Bake until golden brown and edges are set, about 1 hour.
After baking, carefully remove the baking dish from the water.
Transfer to wire rack and let cool at least 1 hour before serving.