1) Preheat the oven to 190C/Gas 5. Place a piece of aluminum foil on the bottom rack to catch any drippings. Butter a 22 by 22-cm glass baking dish and set aside.
2) Place the flour, 30g sugar, lime zest, and 1 tsp salt into the bowl of a food processor and pulse 3 to 4 times. Add the butter and lard and pulse until the mixture just becomes crumbly. Sprinkle or spritz the mixture with the ice water a little at a time and process just until the dough holds together when squeezed in a fist. Place the dough into a large zip top bag and form into a disk. Place the dough into the refrigerator for at least 30 minutes, while you prepare the filling.
3) In a medium mixing bowl whisk together the 200g of sugar, cornstarch, and 1/4 tsp of salt. Stir in the rhubarb, peaches, and lime juice.
4) Remove 1/3 of the dough from the bag, pinch into pieces and distribute evenly in the bottom of the prepared dish. With the remaining dough still in the bag, roll it out to a sheet large enough to cover the top of the dish. Pour the fruit mixture into the dish and top with the dough that has been removed from the bag, pressing the dough into the corners of the dish. Bake, uncovered, for 60 minutes or until the dough is cooked through and starting to turn golden. *If using frozen fruit, increase cooking time to 90 minutes.
5) Change the oven setting to broil and continue to cook until golden brown, approximately 3 minutes. Remove from the oven and allow to stand for 15 to 30 minutes before serving.