How to Make It
Preheat the oven to 350°. Grease and flour two 9-by-2-inch round cake pans. In a medium bowl, sift together the flour, baking powder, cocoa, baking soda, cinnamon and nutmeg.
In a food processor, finely chop the carrots; scrape the carrots into a large bowl. Using an electric mixer, beat in the sugar and salt. Add the eggs, 1 at a time, and beat at low speed until blended. Gradually beat in the oil. Beat in the dry ingredients just until the batter is blended, scraping the sides and bottom of the bowl while mixing.
Pour the batter into the prepared pans and bake for 40 to 45 minutes, or until a tester inserted in the center of the layer cakes comes out clean. Transfer the pans to a rack and let the layers cool completely.
In a medium bowl, combine the sugar, lemon juice, lemon zest and salt and mix at low speed until the sugar is dissolved. Add the mascarpone and beat at low speed until creamy; do not overbeat.
Unmold the layer cakes and center 1 of the layers on a platter. Spread half of the mascarpone frosting on top, leaving a 1/2-inch border around the edge. Top with the remaining cake layer and spread the remaining mascarpone frosting on the top. Garnish with the toasted almonds and lemon zest and serve at room temperature.