Heat oven to 375ºF. Place a piece of aluminum foil on the bottom rack to catch any drippings. Butter a 9-by-9-inch glass baking dish and set aside.
Place the flour, 2 tablespoons sugar, lime zest, and 1 teaspoon 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 1-gallon zip-top bag and form into a disk. Place the dough into the refrigerator for at least 30 minutes while you prepare the filling.
In a medium mixing bowl, whisk together 1 cup of sugar, the cornstarch, and 1/4 teaspoon of salt. Stir in the rhubarb, peaches, and lime juice.
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. Remove the dough from the bag, pour the fruit mixture into the dish, and top with the rolled-out dough, pressing the dough into the corners of the dish. Bake, uncovered, until the dough is cooked through and starting to turn golden, about 60 minutes. If using frozen fruit, increase cooking time to 90 minutes.
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.