Preheat oven to 350 degrees F, line bottom of a 9-inch springform pan with parchment paper, and butter sides of pan.
Melt chocolate and butter together either in a heatproof bowl suspended over a saucepan of simmering water or in a microwave 30 seconds at a time until melted. Set aside to cool slightly.
With electric mixer, beat eggs and sugar together until about tripled in volume, pale, and mousse-like.
Mix almond meal with the cocoa powder. Gently fold into egg mixture, followed by the slightly cooled chocolate mixture. Fold in lime zest and juice.
Pour and scrape into prepared pan. Bake 40 to 45 minutes. The cake will be just firm on top but still have a bit of wobble underneath.
Remove from oven. Cool cake in pan on a wire rack. Once slightly cool, drape a clean kitchen towel over cake to stop it from getting too crusty, though a cracked and cratered surface is to be expected.
When completely cool, loosen cake edges from pan using a metal spatula or knife. Unmold and dust with confectioner's sugar. Serve with Margarita Cream. Makes 6 servings and leftovers.
Whip heavy cream in a separate bowl until it holds its shape. Whisk in the margarita mixture and keep whisking until mixture is light and aerated. Serve immediately with the Flourless Chocolate Lime Cake. Makes 6 (1/4-cup) servings and leftovers.
Stir lime juice, tequila, and triple sec or Cointreau together in a large bowl. Whisk in the confectioner's sugar and let it dissolve in the liquid.