- 6 to 8 plums, choose tart, firm, almost-ripe beauties
- 2 1/4 Cups sugar
- 1/4 Teaspoon kosher salt
- 1/2 Cup water
- 1 1/2 Cup flour
- 1 Teaspoon baking powder
- 10 Tablespoons cold unsalted butter, cut into 3 or 4 chunks
- 3 large eggs
Halve plums along their cleft lines. Pull out stones. Set a rack in the middle of the oven, and heat oven to 350 degrees.
Measure 1 1/4 cups sugar into a heavy 9- or 10-inch skillet, preferably cast-iron.
Stir in salt and water (no more stirring).
Set skillet over medium-high heat.
In about 9 minutes, sugar will begin to color.
Tilt pan, swirling sugar to an even medium-brown.
Pull off heat.
Set plum halves, cut-sides down, into the caramel.
Measure remaining 1 cup sugar, the flour and baking powder into the food processor.
Buzz to combine.
Drop in butter.
Process until crumbly, about 20 seconds.
Slide in eggs, and process until batter comes together, about 10 seconds.
Drop mounds of batter onto the plums.
Using an offset spatula, spread evenly.
Set skillet on a rimmed baking sheet.
Bake until golden and springy, 40–42 minutes.
Let cool, 10 minutes.
Run the spatula around the edge of the pan.
Set a serving platter upside down over skillet.
Using mitts, hold platter and skillet together and invert, landing cake on platter.
Lift away skillet. Enjoy warm or room temperature.