Preheat the oven to 400 degrees F (200 degrees C).

Whisk 1 cup flour and salt together in a bowl; cut in 1/3 cup butter with a pastry blender until mixture resembles coarse crumbs. Add water, 1 tablespoon at a time, until mixture just holds together. Shape dough into a ball; roll out on a floured work surface into a 12-inch circle (crust will be thin). Fold dough gently into quarters; lay into a 9-inch pie plate. Unfold dough; center in the pie plate. Trim crust to 1/2 inch overhang; crimp or flute edges; chill in the refrigerator while making filling.

Combine 1 1/4 cups sugar, 1/3 cup flour, cinnamon, and nutmeg in a bowl; stir in rhubarb and strawberries. Pour filling into crust; sprinkle with pecans.

Combine remaining 1 cup flour and 2/3 cup sugar in a bowl; cut in remaining 1/3 cup butter with a pastry blender until mixture resembles coarse crumbs. Sprinkle crumb topping over pie filling; cover pie edges with aluminum foil strips.

Bake in the preheated oven until crumb topping is golden and filling bubbles around edges, 50 to 60 minutes. Remove foil durng last 10 minutes of baking to brown pie edges.