In a small saucepan, combine lemon juice, water and sugar over medium heat. Bring to a boil, reduce heat and simmer for 2 minutes, stirring occasionally, until the sugar has dissolved. Take the pan off the heat and allow the syrup to cool.;
Whip the cream in a large bowl until thick. Add the cinnamon and 2 tablespoons of the sugar and continue to whip until the cream holds soft peaks. In another bowl, cream together remaining sugar and mascarpone cheese for 30 seconds. Mix 1/4 of the cream into the mascarpone. Using a rubber spatula, fold in the remaining whipped cream. Set aside.
Place the hazelnut liqueur in a small shallow bowl. Dip 16 of the ladyfinger cookies in the hazelnut liqueur and line the bottom of a 13 by 9 by 2-inch serving dish or other decorative serving dish. Spoon any remaining hazelnut liqueur over the dipped cookies. Spread 1/3 of the mascarpone mixture over the cookies. Top with 1/3 of the hazelnuts.
Place the lemon syrup in a small shallow bowl. Dip 16 of the ladyfinger cookies in the syrup and place on top of the hazelnuts. Spread 1/3 of the mascarpone mixture over the cookies. Top with 1/3 hazelnuts. Dip remaining cookies in remaining syrup and place on top. Spoon any remaining syrup over the dipped cookies. Spread with remaining mascarpone and top with remaining hazelnuts and lemon zest.
Cover and refrigerate for at least 6 hours or preferably overnight. Remove the tiramisu from the refrigerator for 1 hour before serving.
Recipe courtesy of Giada De Laurentiis, 2008