Preheat oven to convection 350 degrees fahrenheit.

Put blueberries and sugar in a medium sized saucepan. Add lemon juice at this stage as well (optional).

Stir this mixture of medium low heat until it begins to bubble

To your blueberry jam, add mixture of corn starch + water while it is continuing to boil.

Let this simmer on medium low heat (mix every minute or so) for 3-4 minutes

In a separate bowl mix your butter with a whisk till it turns an off-white color.

Add your sugars into butter and mix till fluffy.

Add vanilla & lemon extract, and lemon juice to this mixture.

Add salt and flour until well incorporated.

Butter a 9x9 square pan with butter and parchment paper. You can use the black binder clips to keep parchment paper down on sides if you choose (make sure whatever clips you use are oven safe).

Flatten about 3/4 of your dough into pan and add blueberry mixture on top. Lastly add your extra dough crumbles on top of blueberry mixture and put in oven for 42-44 minutes!

Let the dessert cool before adding powdered sugar (optional) on top and cutting!

You can store this in the fridge for up to 10 days and in room temperature for 8!