Before you start cooking: Take out 3 medium eggs, ½ cup milk, and 1 cup heavy cream from the fridge an hour before to bring them to room temperature. Grease a baking pan with ½ Tablespoon unsalted butter and dust it with 2 Tablespoons breadcrumbs. Cut 1 ½ pounds pitted plums into small pieces. Preheat the oven to 350 °F.
Make streusel topping: Cut the cold ¾ stick unsalted butter into ¾ cup all-purpose flour, then add ½ cup granulated sugar and ½ teaspoon ground cinnamon. Using your fingertips, work everything into a crumbly mixture.
Let’s bake: Sift 2 ⅓ cups all-purpose flour and 2 teaspoons baking powder into a large mixing bowl. Add 1 cup granulated sugar, heavy cream, milk, 1 Tablespoon lemon zest, and eggs. Start stirring with a fork, then use a hand-held mixer on a lower speed to mix until a semi-liquid batter is created.
Pour the batter into the prepared pan. Spread the plums evenly over the entire surface of the cake. As a final step, sprinkle the crumbly streusel topping on top.
Bake the streusel cake for 30 minutes until golden brown.
Notes
The basic recipe makes about 25 pieces.
Allow the cake to cool, then cut into regular rectangles and serve as a coffee cake on a dessert plate. You can also dust the cake with powdered sugar before serving.
Plums are not essential for this streusel cake. If you don't have plums, substitute other fruits, such as raspberries, strawberries, or grated apples.
The amount of batter in this recipe is enough for a rectangular baking pan about 12x14 inches (30x35 cm). The cake will be relatively thin but moist. If you want a higher layer of batter, use a smaller pan.