Put the blueberries, sugar and lemon juice in a small saucepan with 1tbsp water over a medium heat. Cook for 3-4 minutes until the blueberries have burst and the juices have thickened slightly. Remove from the heat and blend in a food processor until smooth. Set aside.
For the Cheesecake Layer:
Beat the cream cheese, sugar, butter, vanilla, eggs and lemon zest together in a medium bowl until smooth. Set aside.
For the Blondies:
Line a 20 x 20cm square tin with parchment paper. Preheat the oven to 180C or 160C if using a fan oven.
Beat the butter and sugar together until smooth and creamy. Add the eggs and beat until well combined.
Add the flour, salt and baking powder, followed by the vanilla. Mix well to combine. Add the milk and the blueberries and mix until just combined.
Spread the mix into the prepared tin and smooth the top.
Pour the cheesecake mix on top, followed by three lines of the cooled blueberry compote. Drag the tip of a knife through the blueberry compote in a swirling motion, to get a marbled effect.
Bake the blondies in the preheated oven for 25 minutes until set and a knife inserted into the centre comes out clean.
Cool completely for at least 2 hours before slicing into squares to serve.