I've decided that I'm jinxed when I try any cake which includes a "whisk until pale and thick" step. I thought this one might be different because the eggs and sugar were whisked over simmering water, but once again the cake sank (or didn't rise properly) in the centre. The flavour was very good, and the texture was light and moist, and above all, even, throughout the whole cake, so it wasn't a case of underbaking and a soggy centre.
I chose this recipe from Good to Know, but replaced the Amaretto liqueur with elderflower cordial. Instead of putting flaked almonds on top before baking, I left the cake plain, then brushed with another 2 tablespoons of elderflower cordial, and sprinkled lightly with demerara sugar as soon as it was removed from the oven.
The only problem with the recipe was that the cake was still very wobbly in the centre at the end of the cooking time. It needed another 10 minutes baking after the suggested 25 minutes, but was already quite dark, so needed covering with a piece of foil.
The elderflower flavour wasn't really noticeable in the finished cake, but I didn't want to add alcohol, or increase the almond flavour, in this cake.