• Preheat the oven to 350 degrees Fahrenheit.

Filling

• Combine the blueberries in a pot with the sugar and lemon juice. Heat on medium until the mixture begins to bubble.
• Add the cornstarch and water to the mixture and stir together while it continues to boil.
• Let the blueberry filling simmer on low heat for about 5 minutes, stirring every few minutes. Remove from the heat.

Crust

• In a mixer bowl beat the softened butter until it becomes a lighter shade of yellow.
• Add the sugar and brown sugar to the butter and mix until fluffy.
• Add the lemon juice and vanilla extract, mixing together until combined.
• Next beat in the flour and salt. You should have a thick dough.
• Add parchment paper to a 9x9 inch square baking pan.
• Take ¾ of the dough and press it into the bottom of the pan, spreading evenly.
• Then add a layer of the blueberry filling, spreading to cover the dough layer.
• With the rest of the dough, crumble it on top of the blueberry filling.
• Bake for 40-45 minutes.
• Let cool completely before cutting and serving.