The original and authentic Pain de Gênes should be made with almond paste unless I'm much mistaken (and I could be) but this recipe uses ground almonds and no flour. Oddly enough, I first came across this style of Pain de Gênes in my venerable copy of the 1950's classic 'Constance Spry Cookery Book' but since then I've seen a number of French recipes that are made in a similar way. It's a beautifully moist cake with an excellent almond flavour and, even better, it's really easy to make. It works either with afternoon tea or as a dessert with fruit and maybe some creamy substances.
So here's my version of a Pain de Gênes but please note that authenticity is not my strong point.
110 g unsalted butter, softened, plus a bit more for the tin
130 g caster sugar
100 g ground almonds
3 rounded tbsp potato flour
2 tbsp amaretto liqueur
Butter an 18 cm or 19 cm round tin. Preheat the oven to 170°C.
Cream the butter and sugar together thoroughly. Briefly beat in the ground almonds until well combined. Beat in the eggs one at a time. Lightly but thoroughly stir in the potato flour and the liqueur. Pour into the prepared tin, level the mixture and bake for 30 – 35 minutes. A knifepoint inserted in the centre should come out clean. (See, I told you it was easy to make).
Allow the cake to cool in the tin for a few minutes before turning out onto a rack to cool completely. The top of this cake is prone to cracking but I don't mind a few cracks so I don't try to cover them up. As far as I can tell the plain and slightly cracked top is traditional but I've also seen Pain de Gênes decorated with flaked almonds or showered with icing sugar if you feel it needs something.