Upside Down Lemon Pudding Cakes
- Adjust an oven rack to the middle position and heat the oven to 350 degrees. Grease a 2-quart baking dish or six 6-ounce ramekins.
- With an electric mixer on medium-high speed, beat the egg whites to soft peaks. Transfer to a bowl and set aside. Beat the butter and sugar together on medium-high speed until fluffy, about 2 minutes, scraping down the bowl as necessary. Reduce the speed to medium and add the egg yolks, mixing until incorporated. Add the flour, lemon zest, and salt and beat until combined. Add the lemon juice and milk and beat until incorporated. Using a rubber spatula, fold in the egg whites. Pour the batter into the prepared dish or ramekins. Place the dishes in a large baking pan and add enough boiling water to the pan so that it reaches halfway up the sides of the dish or ramekins.
- Bake until the top is golden and the center springs back when gently pressed, 35 to 45 minutes for a large baking dish and 25 to 35 minutes for the individual ramekins. Transfer the dishes to a rack to cool completely, at least 1 1/2 hours. (The pudding cakes can be refrigerated for up to 2 days. Allow to sit at room temperature for 30 minutes before serving.) To serve, run a paring knife around the edges of the dish and invert onto a plate.