Preheat your oven to 350°F (175°C) and prepare a 9-inch springform pan with parchment paper and grease it.

In a large bowl, mix together the dry ingredients: flour, baking powder, salt, brown sugar, granulated sugar, and lemon zest.

Cut in the cold butter until the mixture resembles coarse crumbs.

Add the eggs and vanilla extract to the mixture and stir until just combined.

Press two-thirds of the crumb mixture into the bottom of the pan and refrigerate the remaining mixture.

In a separate bowl, mix the mascarpone, cream cheese, caster sugar, cornstarch, and vanilla until smooth.

Fold in the eggs until just combined, being careful not to overmix.

Layer half of the filling on the crust, sprinkle with blueberries, add the remaining filling, then the rest of the blueberries, and top with reserved crumb mixture.

Bake for 65-75 minutes or until the top is golden brown and a toothpick comes out mostly clean.

Whisk together the powdered sugar and milk for the glaze while the cake cools.

Drizzle the glaze over the cooled cake and let it set before removing from the pan.