If your cakes are very domed, use a slicing knife to trim the tops of the cakes so they are flat. Using a pastry brush, liberally brush the top of each cake with the syrup. Place the first cake on a plate, bottom side up, and spoon half the whipped cream onto the center. Using an offset or regular spatula, push the whipped cream out toward the edges of the cake, without going all the way to the edge. The weight of the second layer will push it the rest of the way. Center the second layer on top of the first, bottom side down, and press down gently to push the whipped cream out slightly. Top with the remaining whipped cream and sprinkle with the lime zest. Either serve or chill immediately.