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 180 degrees C. Melt the butter in a 20x30cm 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 into the buttered baking dish. Scoop peach and raspberry mixture over the batter.
Bake 45 minutes in the preheated oven, until golden brown.