3 large eggs
2 cups whole milk
½ cup sugar
¼ tsp. pure vanilla extract
⅛ tsp. salt
5 Tbsp. unsalted butter, melted and cooled
¾ cup all-purpose flour
1 cup pitted prunes
⅓ cup dark raisins
1 cup hot tea, such as Earl Grey, or ¼ cup Armagnac plus ¼ cup water
~ Confectioners’ sugar, for dusting
Steps

Up to one day ahead: Put the eggs, milk, sugar, vanilla, salt, and melted butter in a blender or food processor and whir for 1 minute to blend. Add the flour and pulse the batter several times. Pour the batter into a pitcher, cover, and refrigerate for at least three hours, or, preferably, overnight.
Meanwhile, for tea-soaked fruit, put the fruit in a heatproof bowl and pour over the hot tea. When the tea cools to room temperature, cover. For Armagnac-soaked fruit, put the fruit and water in a small saucepan over medium heat. Cook until the water almost evaporates, then turn off the heat and pour the Armagnac evenly over the fruit. Stand back, ignite the alcohol with a long match, and wait until the flames die out before pouring the fruit and syrup into a heatproof bowl. When the fruit is cool, cover it and set aside.
Getting ready to bake: Center a rack in the oven and preheat the oven to 375 degrees. Butter an 8-by-2-inch round cake pan, line the bottom with parchment or waxed paper, butter the paper, and dust the pan with flour, tapping out the excess. Put the pan on a baking sheet.
Remove the batter from the refrigerator and whisk to reblend it, then rap the pitcher against the counter to break the top bubbles. Pour the batter into the pan and drop in the fruit, trying to distribute it fairly evenly; discard whatever soaking syrup remains.
Bake for 50 to 60 minutes, or until the top of the cake is puffed and brown and a thin knife inserted into the center comes out clean. Transfer the pan to a cooling rack and cool to room temperature.
The far is fragile (its fragility is part of what makes it so delicious) and it takes a little extra TLC to unmold it. So that the custard is not cut by the wires of the cooling rack, cover the rack with a piece of parchment or waxed paper, and dust the paper with confectioners’ sugar. Have a serving plate at hand. Run a blunt knife gently between the cake and the sides of the pan, and turn the cake out onto the prepared rack. Don’t leave it on the rack any longer than necessary — quickly and gently invert it onto the serving plate.
Just before serving, dust the cake with confectioners’ sugar.