Preheat oven to 375 F. In a large bowl, toss peaches with lemon juice. Add 3/4 cup sugar and 2 tablespoons flour and toss to coat. Butter a 13×9 baking dish and spread peaches evenly on bottom.

In a large mixing bowl, combine flour, salt, and baking powder. In a separate bowl or stand mixer, cream together remaining 1/4 cup sugar and butter for about 2 minutes or until light and fluffy. Add eggs, 1 at a time, beating after each one. Add vanilla and stir to combine. Slowly add flour mixture and buttermilk a little at a time to the butter mixture, beginning and ending with the flour mixture. Stir just until combined. Fold in blueberries.

Pour batter over peaches and spread evenly. Sprinkle with sugar. Line a baking dish with foil {or you can line with a Silpat}, place baking dish on pan and bake for 1 hour or until golden brown.