1. First prepare your peaches. Begin by peeling them (you can do this by cutting a cross into each peach, placing it in a pot of boiling water until the skin begins to peel off itself where you made the cross, and then place it into a bowl of ice water). Once you’ve peeled your peaches, cut them into thin slices.
2. Preheat your oven to 425 deg F and grease your baking dish. Place the sliced peaches in a large bowl, and add the sugar, ground cinnamon, lemon juice and flour. Mix well and transfer into your baking dish. Bake for 10 minutes, then take it out of the oven and spoon your topping on.
3. While the peaches are baking, prepare the topping. Combine flour, white sugar, brown sugar, baking powder and salt, then add the butter and mix until the mixture resembles coarse meal. At the end, pour in the boiling water and whisk until you get a nice, smooth batter.
4. Take the baking dish with the peaches out of the oven, and spoon the topping over the peaches evenly. Sprinkle with the cinnamon sugar (I ended up using only about half of it), and bake for 20 minutes, until the top is golden brown. Serve warm with vanilla ice-cream!