Preheat oven to 350 degrees Fahrenheit and grease an 8x8 inch baking pan.

In a bowl, combine flour, 0.5 cups sugar, and salt. Cut in cold butter using a pastry cutter until the mixture resembles coarse crumbs.

Press 2 cups of the crumble mixture firmly into the bottom of the prepared pan and bake for 10 minutes.

While the crust bakes, beat the cream cheese, remaining 0.25 cups sugar, egg, and vanilla extract until smooth.

Spread the cream cheese mixture evenly over the pre-baked crust.

In a small bowl, toss the blueberries with lemon juice and spread them over the cream cheese layer.

Sprinkle the remaining crumble mixture over the blueberries.

Bake for 35 to 40 minutes until the top is golden brown and the filling is set.

Cool completely in the pan, then refrigerate for at least 2 hours before slicing into 12 bars.