The bittersweet flavor of this almond paste-based cake complements the slight acidity of the lemon perfectly. Small portions are in order—this is a rich cake.
Set a rack at the middle level of the oven and preheat to 325 degrees.
For the cake, cut the almond paste into 1-inch cubes and place in a mixing bowl with the sugar and 1 egg. Beat with a paddle (if you have one) on low speed until smooth. Beat in the