Preheat oven to 375 degrees.
Prepare a 8x8 baking dish by lining it with foil or parchment paper. Then, spray the lining and allow the edges to overhang for easy removal.
In a large bowl, add the sugar, flour, baking powder and salt and mix until combined.
Then, add the egg and vanilla. Mix well.
In a medium bowl, add the butter and flour. Cut the butter into the flour mixture until it is crumbly.
Take half of the flour mixture and pack it down in the bottom of your pan.
In a small bowl, add your diced strawberries, 1/3 cup sugar and cornstarch. Mix until the mixture is gooey.
Pour over the top of your bottom layer in the pan and spread out evenly.
Pour the rest of your flour mixture evenly over the top of your strawberries.
Bake for 35-40 minutes, until the top is golden brown. Allow to cool completely before cutting.