As walnut cakes go, this must be the simplest and most essential of them all. The cake itself is made of just three ingredients–walnuts, eggs and sugar. A little lemon zest adds a delicate, fresh aroma and powdered sugar makes it pretty.
It's a traditional cake from Calabria in southern Italy–the sort of cake that was born out of age-old peasant traditions; the sort of cake that your nonna might whip up and have sitting on her kitchen bench, ready to be offered to guests with a short, dark stove-top espresso for breakfast or an afternoon snack. Yes, cake for breakfast.
This walnut cake seems rather humble when compared to other Calabrian sweets, which have a tendency to be deep fried, filled with custard or jam, and covered in honey, dark chocolate, or sprinkles.
This cake, however, is elegant in its simplicity and so incredibly moist–it reminds me of the Spanish Tarta de Santiago Almond Cake. The walnuts are pulverized in the food processor, so it's chunkier and a little more rustic than a cake made with almond meal. In my opinion, it needs nothing more than a dusting of powdered sugar.
This recipe is taken from a 1960s volume of Italian Regional Cooking by Ada Boni, who suggests splitting the cake and sandwiching it with a light lemon butter icing. It remains moist for several days–if it isn't eaten all by then.
**** An update to this recipe 11/9/14 ****
After reading a couple of comments that people have had difficulty with this cake (removing it from the pan, crumbling, being underdone inside), I wanted to retest this recipe again and offer some more advice–including testing the suggestion by the original author of this recipe, Ada Boni, who advises to fill this cake with a lemon buttercream. So–first, some better description on the texture of this cake. It is a very moist cake, it may even appear underdone to some – but do not fear. Let it rest a day. This cake is possibly even better a day or two old.
Secondly, I would advise using baking paper to line your cake tin. Use springform if you prefer. Bake as described (I actually find personally that this cake cooks better at a slightly lower temperature, around 350F as walnuts–like a lot of nuts–have a tendency to burn easily). Remove from the oven when the top of the well-browned cake is firm to the touch. Let the cake cool in the tin before removing from the tin. Wrap in plastic wrap and place in the refrigerator until chilled. This seems to give it a bit of time to settle and will be easier to handle. It will still crumble a little when slicing but if you are careful, you won't have any problem getting pretty, nice slices.
Now on to the buttercream. This is a WONDERFUL idea! It's even better than the cake on its own, lifts it to something extra special. I followed a couple of recipes I found online for lemon buttercream using 2 egg whites, 1/2 cup of sugar, 1 stick of butter and the zest of 1 lemon. Whip the whites with the sugar over a double broiler for a few minutes minutes or until the mixture is warm and you can no longer feel the sugar granules if you rub it between your fingers. Remove from heat, beat 8 more minutes or until mixture has returned to room temperature. Slowly add the butter bit by bit, beating all the way until you have a glossy, smooth buttercream. Add zest and chill the mixture. Carefully cut the cake in half so you have two thin discs (this is a little tricky with a crumbly cake but if the cake is well-chilled it is easier). Fill with about half of the buttercream mixture. Place the top disc on top and cover the rest of the cake with the rest of the icing (I covered the top and just did a "crumb coat" around the sides). I topped it with some diced candied fruit for decoration but it's lovely just as it is. This lemon buttercream is a great pairing for this cake and it also is wonderfully forgiving as it hides any flaws, including crumbling, splitting or even an inside that might seem too soft/moist – it's hard to describe but the buttercream just holds it all together in the most amazing way! It also keeps very well for a few days and holds together very, very nicely. So for anyone else having a little trouble handling this flourless cake, I would highly recommend trying the lemon buttercream filling!
Ingredients3/4 pound (340 grams or about 3 cups) shelled walnuts
4 eggs, separated
1 cup (225 grams) caster sugar (superfine sugar)
Finely grated zest of 1 lemon
Confectioners\' sugar for dusting