A cobbler-meets-cake spring dessert: jammy stewed strawberries and rhubarb bubble up under a tender mascarpone-enriched cake batter. Serve warm with whipped cream or ice cream.
Preheat the oven to 350°F (175°C). Butter a baking dish of about 1.5-quart (1.4 L) capacity — an oval 10 x 8 x 2-inch dish works. Cooking time varies with the dish, so watch carefully.
In a large saucepan over medium heat, combine the rhubarb, water and 1/2 cup sugar. Cook 10 minutes, stirring occasionally, until the sugar is bubbling and the rhubarb has softened slightly. Stir in the strawberries. Spread in the buttered dish and set aside.
In a medium bowl, whisk together the flour, baking powder and salt. Set aside.
In a stand mixer, beat the butter and 3/4 cup sugar until light and fluffy, about 3 minutes. Beat in the eggs one at a time, beating 1 minute after each. Beat in the mascarpone (or cream cheese) and vanilla.
With the mixer on low, add 1/3 of the flour mixture and beat to combine, then add 1/2 of the milk and beat again. Repeat, finishing with the flour mixture.
Spoon the cake batter over the strawberry-rhubarb mixture, smoothing the surface with the back of the spoon. Sprinkle with 1 tbsp sugar and bake 45–55 minutes, until golden brown and a toothpick inserted in the top inch of the centre comes out clean.
Notes
Dish size is flexible: Any ~1.5-quart baking dish works; a deeper dish bakes longer, so watch and test for doneness.Mascarpone or cream cheese: Either adds richness and a tender crumb — use whichever you have on hand.Doneness cue: The fruit bubbles up the sides, so test the cake itself in the top inch of the centre with a toothpick.Serving: Best warm or at room temperature with whipped cream or vanilla ice cream.