Make the Citrus Caramel 

Combine the granulated sugar and 6 tablespoons of water in a small saucepan. Cover and bring to a boil over medium-high heat; continue booking for 1 minute until the sugar dissolves. 

Uncover and continue boiling, gently swirling the pan as the color of the caramel develops around the edges. After 3-4 minutes, the sugar mixture will have turned a medium shade of amber and become fragrant. Remove from the heat and carefully add the orange zest, juice, and remaining 1/2 cup water all at one time. The mixture will sputter and steam, so use caution. Stir until smooth; if necessary, return the pan to low heat to liquefy completely. Transfer to a shallow, heatproof container and set aside for 10 minutes to cool slightly.

Make the Mascarpone Whipped Cream

In the bowl of a stand mixer, whip the mascarpone cheese, heavy cream, powdered sugar, and pinch of salt on medium-high speed until stiff peaks form. 

To assemble the Red, White, and Blue Dessert Cake.

Working one at a time, use tongs to dip 5 of the ladyfingers in the citrus caramel carefully. Turn the ladyfinger to fully coat, then hold over the bowl to allow the excess to drip back in.

Place the ladyfingers one at a time next to each other in a snug row on a serving platter. Spread a thin layer of the mascarpone whipped cream over the layer of the top of the ladyfingers. Top with one-third of the fruit in a single layer. 

Repeat dipping and layering twice more. Cover loosely but fully refrigerate for at least 24 hours and up to 2 days before serving. 

To serve, top with more halved or whole berries and then slice between each row of ladyfingers. Each slice can then be halved down the middle easily creating 2 servings per slice.