With its pink rhubarb top, this light and fluffy cake is almost too pretty to eat! Tip: Eggs at room temperature whip up better than cold ones, so take them out of the fridge ahead of time.
- Prep time 1 hour & 30 minutes
- Total time 5 hours & 45 minutes
- Portion size 16 servings
Filling: In large saucepan, bring rhubarb, sugar, cornstarch, lemon juice and 1/4 cup water to boil over medium-high heat. Reduce heat to medium; simmer, stirring and pressing on rhubarb with back of spoon, until tender, thickened and glossy, about 5 minutes. Strain through fine- mesh sieve into bowl, pressing gently on solids with back of spoon. Place plastic wrap directly on surface; refrigerate until chilled, about 4 hours. (Make-ahead: Refrigerate for up to 2 days.)
Cake: While filling is chilling, grease two 8-inch (1.2 L) round cake pans; line bottoms with parchment paper. Set aside.
In stand mixer with whisk attachment, beat eggs on medium-high speed until foamy. Gradually beat in sugar, 2 tbsp at a time, until mixture is thick, tripled in volume, glossy and pale yellow, about 10 minutes. Beat in lemon zest and vanilla. In bowl, whisk together flour, baking powder and salt; fold into egg mixture in 3 additions. (Do not overmix or batter will deflate.) Stir 1 cup of the batter with butter until smooth; fold back into batter just until combined. Scrape into prepared cake pans, smoothing tops. Bake in 350°F (180°C) oven until cake is golden, pulls away from edge of pan and springs back when surface is gently pressed, 25 to 30 minutes. Let cool in pans for 10 minutes. Invert onto racks; let cool completely. Peel off parchment paper.
Mascarpone Icing: In large bowl, beat mascarpone with butter until smooth. Beat in vanilla. Beat in icing sugar, one-third at a time, until smooth.
Assembly: Remove 1/2 cup of the filling to small bowl; set aside. Cut cakes in half horizontally to make 4 layers. Place 1 bottom layer, cut side up, on cake plate; slide strips of waxed or parchment paper between edge of cake and plate (to keep plate clean). Spread half of the remaining filling over cut side, leaving 1/2-inch (1 cm) border. Spread 3/4 cup of the icing over second cake layer; arrange, icing side up, over top of first layer. Top with third cake layer; spread remaining filling over top, leaving 1/2-inch (1 cm) border. Top with remaining cake layer, cut side down.
Using offset palette knife, spread 1 cup of the icing all over cake to seal in crumbs; refrigerate until firm, about 30 minutes. Spread remaining icing all over cake. Spoon reserved filling over top, leaving 1/2-inch (1 cm) border. Discard waxed paper strips. Refrigerate until firm, about 30 minutes.
Nutritional facts per serving: about
- Sodium 111 mg
- Sugars 60 g
- Protein 5 g
- Calories 439.0
- Total fat 16 g
- Potassium 113 mg
- Cholesterol 99 mg
- Saturated fat 10 g
- Total carbohydrate 71 g
- Iron 6.0
- Folate 13.0
- Calcium 7.0
- Vitamin A 14.0
- Vitamin C 7.0