Preheat oven to 350.
In bowl whisk together your melted butter and brown sugar, spread on the bottom of a 9" high sided pan or springform pan, set aside.
Top with your blueberries and set aside.
In a large bowl whisk together your flour, baking powder and salt, set aside.
In another bowl beat together butter, sugar, egg and vanilla until combined.
Add in your dry ingredients and beat until combined.
Lastly add in your milk and beat until incorporated.
Spoon over blueberries and gently spread over the top using an offset spatula.
Bake in oven for about 35-40 minutes until golden and toothpick comes out clean.
Remove from oven and let cool in pan 5-10 minutes before flipping out onto serving tray.
Cut and serve warm or cool.