Preheat oven to 175°C (350°F) and grease two 20cm round cake pans.
Cream butter and 200g sugar until pale and fluffy, then beat in eggs one at a time.
Sift flour and baking powder; alternate adding dry ingredients and milk to the butter mixture.
Divide batter into pans and bake for 25-30 minutes until a tester comes out clean.
In a saucepan, simmer raspberries, 50g sugar, and lemon juice until thickened; let cool completely.
Whisk mascarpone, heavy cream, powdered sugar, and vanilla until stiff peaks form.
Place first cake layer on a stand, pipe a cream border, fill with raspberry compote, and top with more cream.
Place second cake layer on top and cover the entire cake with the remaining mascarpone cream.