4 tablespoons (1/2 stick) unsalted butter at room temperature
1 cup sugar
1 tablespoon finely grated meyer (or regular) lemon zest
3 large eggs, at room temperature, separated
1/3 cup meyer lemon juice
1/3 cup all-purpose flour
8 oz sour cream
1/4 teaspoon salt
Powdered sugar for dusting
Preheat the oven to 350F/180C. Butter a 1-qt. (1-ltr) souffle dish. Have ready a large baking pan which will accommodate your souffle dish.
Beat the butter at medium speed until light. Add the sugar and zest and beat until combined. Add the egg yolks, one at a time, beating well after each addition. Reduce speed to low and add half the lemon juice, half the flour and half the sour cream and beat until smooth; repeat with remaining lemon juice, flour and sour cream.
Beat the egg whites at medium speed until foamy. Increase speed to medium-high, add the salt, and beat to stiff peaks. Add one-quarter of the whites to the lemon mixture and gently fold in. Continue to fold in whites one-quarter at a time. Transfer it to the prepared souffle dish. Place the dish in the larger pan and carefully pour boiling water around it to a depth of 1 inch (2.5cm).
Bake for 50 minutes to an hour, until the top is golden brown, the center is just set, and the top springs back when lightly touched. Remove from the water bath and cool on a rack for 10-15 minutes.
Lightly dust with powdered sugar before serving (I didn’t bother) and serve warm, scooping up some of the pudding at the bottom of the dish along with the cake.