01 - Combine water, granulated sugar, lemon juice, and zest in a small saucepan. Heat over medium heat, stirring constantly until sugar completely dissolves. Remove from heat and allow to cool completely before using.
02 - In a chilled mixing bowl, beat cold heavy cream and powdered sugar with electric mixer until stiff peaks form. Set aside.
03 - In separate bowl, whisk softened mascarpone cheese, vanilla extract, and lemon zest until smooth and creamy.
04 - Gently fold whipped cream into mascarpone mixture until fully incorporated and fluffy. Be careful not to overmix.
05 - Quickly dip each ladyfinger into cooled lemon syrup, working rapidly to prevent oversaturation. Cookies should be moistened but not soggy.
06 - Arrange half of dipped ladyfingers in single layer in 9x9-inch dish. Spread half of mascarpone cream evenly over cookies.
07 - Repeat with remaining ladyfingers and remaining mascarpone cream. Use spatula to smooth top surface evenly.
08 - Cover dish tightly with plastic wrap. Refrigerate minimum 4 hours, preferably overnight, to allow flavors to meld and texture to set properly.
09 - Before serving, garnish with fresh lemon slices and additional lemon zest if desired. Serve chilled.