Spiced Plum Cake with Toffee Glaze
One 9-inch (23cm) cake, about ten servings
Purple plums aren’t usually sold by variety in France, but tart ones work best, such as Santa Rosa plums. You could use other kinds of plums, such as Italian prune plums (quetsches), although I prefer to use the tartest ones I can find. If you wanted to experiment with other types of fruit, this cake probably lends itself to others. The toffee is drizzled over the top in a modest quantity. But if you are a toffee-lover, you can certainly double the amount and really go for it. Buttermilk is called lait ribot or lait fermentè in France and is available in some supermarkets and Arab markets. You can make a good substitute by using a scant 1/2 cup (125ml) of whole milk with a teaspoon of lemon juice or white vinegar added. Let stand for 10 minutes, then use the soured milk just like buttermilk.
Topping
5 medium plums (12 ounces, 340g)
1 cup ( 85g) sliced almonds blanched or unbalanced
2 tablespoons flour
1/3 cup (60g) packed light brown sugar
1/2 teaspoon ground cinnamon
1/2 teaspoon ground cardamom
2 tablespoons melted butter salted or unsalted
Cake
8 tablespoons (4 ounces, 115g) unsalted butter, at room temperature
3/4 cup (150g) granulated sugar
1 1/2 cups (175g) flour
1/2 teaspoon baking powder, preferably aluminium-free
1/2 teaspoon baking soda
1 1/2 teaspoons ground cardamom
1/2 teaspoon salt
2 large eggs, at room temperature
1 teaspoon vanilla
1/2 cup (125ml) buttermilk (see headnote)
Toffee Glaze
2 tablespoons butter, salted or unsalted
3 tablespoons dark brown sugar
3 tablespoons heavy cream
pinch of salt
1/4 teaspoon vanilla extract
1. Preheat the oven to 350ºF (180ºC). Butter a 9-inch (23cm) springform cake pan.
2. Halve, pit, and cut the plums into 8 slices.
3. In a small bowl, make the topping by mixing together the sliced almonds, 2 tablespoons flour, light brown sugar, 1/2 teaspoons (each) cinnamon and cardamom, and melted butter, until everything is evenly mixed. Set aside.
4. In the bowl of a stand mixer fitted with the paddle attachment, or by hand in a medium bowl, beat the butter and sugar until light and fluffy, about 3 to 5 minutes.
5. In a separate bowl, whisk together the flour, baking powder, baking soda, 1 1/2 teaspoons ground cardamom, and salt.
6. Add to the eggs to the creamed butter one at a time, scraping down the sides of the bowl after each addition to make sure they’re mixed in. Add the vanilla extract. Stir in half of the dry ingredients, then the buttermilk, then the rest of the dry ingredients, mixing just until combined. Do not overmix.
7. Spread the batter into the prepared cake pan. Strew the plums over the top in an even layer, then spread the almond topping over the plums. Bake until the center just feels set, about 55 minutes to one hour. (A toothpick inserted into the center should come out clean of any cake batter.) If the top is browning too fast, drape a sheet of aluminum foil over the cake pan and finish baking. Let the cake cool completely then remove the sides of the springform pan.
8. To make the toffee glaze, mix the butter, dark brown sugar, cream, salt, and vanilla in a small saucepan Bring to a boil, stirring gently. Reduce the heat and cook at a low boil for 1 minute. Remove from heat and drizzle the toffee over the cake.

Serving: The cake is best served at room temperature. It can be served without accompaniment, or with a dollop of whipped cream or vanilla ice cream.

Storage: The cake will keep for up to three days at room temperature. I would not recommend freezing it.