Preheat the oven to 180 C / Gas 4. Grease a deep 23cm round pie dish.
Whisk plain flour, ground almonds, baking powder and salt together in a medium bowl.
Whisk ricotta cheese and milk together in a small bowl until smooth.
Beat butter with an electric mixer until creamy. Add sugar and beat until very light, about 3 minutes. Add vanilla and almond extracts; beat until blended. Scrape down sides with a spatula. Add eggs one at a time, beating well after each addition.
Pour mixture into the prepared baking dish. Smooth the top with the spatula. Sprinkle strawberries and blueberries over the top. Press very gently into the cake. Sprinkle demerara sugar on top.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, about 70 minutes. Cover with foil when top starts to brown. Cool completely on a rack before slicing.
The mixture will fit well in a larger baking dish, but avoid using a smaller one. If you don't have a deep pie dish, try splitting the mixture between 2 shallower dishes. Reduce baking time if baking in a larger or shallower dish.