Preheat the oven to 350 degrees F (175 degrees C). Grease and flour a 9-inch springform pan.

To make the blueberry topping: Combine blueberries, sugar, flour, and lemon zest in a bowl. Toss until blueberries are coated, then pour into the prepared pan.

To make the cake: Cream sugar and butter in a large bowl with an electric mixer until light and fluffy. Beat in eggs, one at a time, then stir in lemon zest and almond extract.

Stir flour and baking powder together in a small bowl; beat into butter mixture alternately with milk, mixing just until incorporated. Pour cake batter over blueberries in the pan.

Bake in the preheated oven until a toothpick inserted into the center of the cake comes out clean, 60 to 70 minutes. Place a serving plate over the top of the pan and carefully invert the cake and plate together so the berries end up on top. Carefully unlock the buckle on the side of the pan and remove. Sprinkle toasted almonds on top of the cake and serve warm.