Preheat the oven to 325F (160C). Butter two shallow 10-inch (23cm) cake pans and line each with a circle of parchment paper. Then lightly butter the top of each circle of paper.
Beat the butter, sugar and salt until smooth.
Meanwhile, pulverize the nuts and flour in a food processor or blender until relatively fine, but not powdery. If you don’t have a machine, simply chop the nuts by hand and toss them with the flour.
Beat in the eggs one at a time. Afterwards, stir in the ground nut mixture and the carrots, mixing just until smooth.
Divide the batter into the pans, smooth it evenly, and bake for 40 minutes, until a toothpick inserted into the center comes out clean.
Cool, then release the cake from the pans and cut in wedges to serve.