Preheat oven to 350°. Set 6 ramekins (2/3 cup size) in a 9- by 13-in. baking pan.
In a medium bowl, whisk together egg yolks and granulated sugar until thick and creamy. Whisk in flour, butter, lemon zest and juice, and milk until blended.
In a deep bowl with a mixer on high speed, beat egg whites and cream of tartar until whites hold stiff, moist peaks when beater is lifted. Stir one-quarter of whites into yolk mixture until blended, then gently fold in remaining whites. Gently fold in half of raspberries.
Spoon batter into ramekins. Pour enough hot tap water into baking pan to come 1 in. up sides of ramekins.
Bake until cake layers are set and tops are golden, 30 to 35 minutes. Remove ramekins from water; let cool at least 30 minutes. Serve with more berries on top and a dusting of powdered sugar.
Make ahead: Chill airtight up to 1 day; pudding layer will become more distinct.
Note: Nutritional analysis is per serving.