For the apple mixture, peel, halve, core and slice the apples into wedges. Combine apples, blackberries and remaining ingredients and place in a 9 by 13 by 2-inch baking dish. For the topping, melt the butter and pour into a bowl. Stir in sugars. Combine flour with cinnamon and baking powder and stir to mix; stir into butter and sugar mixture. Stir in pecans. Separate the topping mixture into large crumbs and distribute over the top of the apple mixture. Bake at 375 degrees about 45 minutes, until bubbling and well browned. Serve warm or at room temperature.