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Brown butter plum upside-down cake topped with overlapping caramelized purple plum wedges and one cut slice showing the tender crumb

Brown Butter Plum Upside-Down Cake with Caramelized Plums

A 9-inch upside-down cake with a glossy layer of caramelized plums over a tender almond crumb flavored with nutty brown butter. Resting the baked cake for 15 minutes before inversion lets the topping settle while the caramel remains fluid enough to release cleanly.
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Prep Time 30 minutes
Cook Time 55 minutes
Cooling 1 hour 15 minutes
Total Time 2 hours 40 minutes
Servings: 10 slices
Course: Dessert
Cuisine: American
Calories: 397
Ingredients Equipment Method Notes

Ingredients
  

  • 28 g unsalted butter 2 tablespoons, melted, for the fruit topping
  • 90 g light brown sugar about 7 tablespoons, packed, for the fruit topping
  • 500 g ripe but firm plums pitted weight, cut into wedges about 8 mm thick
  • 170 g unsalted butter 3/4 cup, cut into pieces, for browning and using in the cake batter
  • 200 g all-purpose flour about 1 2/3 cups, spooned and leveled if not weighed
  • 40 g finely ground blanched almond flour about 1/3 cup
  • 6 g baking powder 1 1/2 teaspoons
  • 3 g fine sea salt 1/2 teaspoon
  • 150 g granulated sugar 3/4 cup
  • 2 large eggs about 100 g without shells, at room temperature
  • 10 g pure vanilla extract 2 teaspoons
  • 120 g full-fat sour cream 1/2 cup, at room temperature
  • 60 g whole milk 1/4 cup, at room temperature

Equipment

  • 9 x 2-inch solid round metal cake pan
  • Parchment paper
  • Digital kitchen scale
  • Small light-colored saucepan
  • Heatproof bowl
  • Large and medium mixing bowls
  • Fine-mesh sieve
  • Balloon whisk
  • Flexible silicone spatula
  • Offset spatula
  • Wire cooling rack
  • Flat serving plate at least 10 inches wide

Method
 

  1. Heat a conventional oven to 350°F (175°C) with a rack in the lower-middle position. Trace the base of a solid 9 x 2-inch metal cake pan onto parchment and cut out the circle. Lightly grease the pan sides, fit the parchment snugly over the bottom, and set the pan on a dry work surface. Avoid a springform pan because the warm butter and sugar topping can leak through its seam.
  2. Place the 170 g butter in a small light-colored saucepan and melt it over medium heat. Continue cooking for 5 to 7 minutes, swirling frequently as the butter foams and crackles. Remove it from the heat when the foam subsides, the milk solids are deep golden brown, and the aroma is distinctly nutty. Immediately scrape the butter and every browned particle into a heatproof bowl. Cool for about 15 minutes, until fluid but only barely warm.
  3. Pour the 28 g melted butter over the parchment-lined pan and tilt the pan to coat the base. Sprinkle the brown sugar evenly over the butter, breaking up firm lumps with your fingertips. Arrange the plum wedges skin-side down in tight, slightly overlapping concentric circles, filling the center with smaller pieces. Keep the fruit in one even layer rather than stacking it, which helps the cake bake level and limits pools of uncooked juice.
  4. Set a fine-mesh sieve over a medium bowl and add the all-purpose flour, almond flour, baking powder, and salt. Sift the mixture, then whisk for about 20 seconds to distribute the almond flour and leavener evenly. Break apart any almond flour clumps that remain. This even distribution matters because concentrated pockets of almond flour can turn pasty beside the fruit, while uneven baking powder can leave tunnels in the crumb.
  5. In a large bowl, whisk the cooled brown butter and granulated sugar for 45 seconds; the mixture will look glossy and slightly grainy rather than creamed. Whisk in the eggs one at a time, mixing thoroughly after each, then add the vanilla. Whisk in the sour cream until smooth, followed by the milk. The mixture should be cohesive and satiny. If small butter flecks appear, let the bowl stand in a warm spot for 2 minutes and whisk again.
  6. Add the dry mixture to the wet ingredients in two additions, folding with a flexible spatula just until no flour streaks remain. The batter should be thick, smooth, and able to fall slowly from the spatula. Spoon it gently over the plums, then spread it to the edge without disturbing the pattern. Bake for 47 to 52 minutes, until the center springs back, the top is golden, and a tester inserted in the center returns with moist crumbs but no wet batter.
  7. Transfer the pan to a wire rack and leave the cake undisturbed for exactly 15 minutes. Run a thin offset spatula around the side without cutting toward the fruit. Center a flat serving plate over the pan, protect your hands with dry oven mitts, and invert both in one confident motion. Wait 30 seconds before lifting the pan, then peel away the parchment. Reposition any attached plum gently and cool for at least 1 hour before slicing with a sharp knife.

Notes

  • Choose plums that yield slightly near the stem but still hold their shape when sliced. Rock-hard plums remain sharply tart, while overripe ones can collapse and release enough liquid to soften the cake’s surface.
  • Use a light-colored saucepan for browning the butter. A dark interior hides the changing milk solids, making it much easier to move from toasted brown to bitter black.
  • Arrange the plums tightly because they shrink as they bake. Leaving large spaces exposes patches of brown sugar that can harden instead of becoming a fruit-enriched caramel.
  • Do not pour hot brown butter directly into cold eggs or sour cream. Cooling the butter and tempering the dairy to room temperature protects the emulsion and gives the cake a uniform crumb.
  • Set a timer for the 15-minute inversion window. Turning the cake out immediately risks tearing its delicate hot crumb, while leaving it in the pan too long allows the caramelized fruit to adhere.