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Key lime tiramisu scooped out with a spatula.
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Key Lime Tiramisu

Key Lime Tiramisu is a citrus version of the classic Italian dessert. It’s no-bake, rich, and creamy, but each bite is bright with plenty of tart key lime flavor.
Prep Time30 minutes
Chill Time6 hours
Total Time6 hours 30 minutes
Servings: 15 slices
Calories: 456kcal
Author: Karin and Ken

Ingredients

Key Lime Mascarpone Filling

  • 16 oz mascarpone cheese cold
  • 3 cups heavy whipping cream cold
  • 1 cup powdered sugar
  • ½ cup key lime juice
  • 1 tablespoon lime zest
  • 1 teaspoon vanilla extract

Lime Soak

Layers

  • 2 packages ladyfinger biscuits about 40–44

Garnish

  • Extra lime zest
  • Optional: thin lime slices for garnish

Instructions

For the lime soak

  • In a small saucepan over medium heat, combine water and sugar.
  • Stir until the sugar fully dissolves, then remove from heat.
  • Stir in the key lime juice and lime zest.
  • Let cool completely before using.

For the mascarpone filling

  • In a large mixing bowl, add mascarpone, heavy whipping cream, powdered sugar, key lime juice, lime zest, and vanilla extract.
  • Using a hand mixer, beat on medium-high speed until the mixture thickens and holds soft to medium peaks. The filling should be smooth, creamy, and spreadable.
  • Be careful not to overmix, once thickened, stop mixing to avoid a grainy texture.

To assemble

  • Quickly dip each ladyfinger into the cooled lime soak (do not soak too long or they will become soggy).
  • Arrange a single layer of soaked ladyfingers in the bottom of a 9x13 inch baking dish.
  • Spread half of the mascarpone filling evenly over the ladyfingers.
  • Repeat with another layer of soaked ladyfingers, then spread the remaining filling on top.
  • If desired, transfer some of the filling into a piping bag fitted with a large star tip.
  • Pipe dollops or decorative swirls across the top of the tiramisu.
  • Finish with a sprinkle of fresh lime zest over the top.
  • Cover and refrigerate for at least 6 hours, preferably overnight, to allow the layers to set and flavors to develop.

Notes

  • If the key lime tiramisu is runny, the ladyfingers may have been oversoaked, or the dessert did not chill long enough. Dip the ladyfingers quickly and chill for at least 6 hours, preferably overnight. 
  • Mix the filling only until medium-soft peaks form, as overmixing can cause the mascarpone mixture to separate and become grainy. 
  • For the best consistency, use the heavy cream and mascarpone straight from the refrigerator. 

Nutrition

Calories: 456kcal | Carbohydrates: 34g | Protein: 6g | Fat: 33g | Saturated Fat: 20g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 5g | Cholesterol: 142mg | Sodium: 70mg | Potassium: 95mg | Fiber: 0.3g | Sugar: 16g | Vitamin A: 1278IU | Vitamin C: 5mg | Calcium: 89mg | Iron: 1mg