In a bowl, mix the peaches, raspberries, 1/4 cup sugar, cinnamon, and lemon juice. Allow to sit while proceeding with remaining steps.
Preheat oven to 350 degrees F (175 degrees C). Melt the butter in a 9x13 inch glass baking dish in the preheating oven, and evenly coat dish. Remove from heat.
In a bowl, mix the flour, baking powder, salt, and 1 cup sugar. Mix in milk just until dry ingredients are evenly moist. Pour evenly into the buttered baking dish. Scoop peach and raspberry mixture over the batter.
Bake 45 minutes in the preheated oven, until golden brown.