2/3 cup rice flour
1/3 cup almond meal
1/4 cup arrowroot powder
1/4 teaspoon xanthum gum
1/2 teaspoon sugar
1/4 teaspoon coarse salt
7 tablespoons coconut oil, solid but not refrigerated
3 tablespoons ice water
1 1/2 teaspoons apple-cider vinegar
2 1/2 cups (about 3 large stalks) rhubarb, slices 1/4-inch-thick
2 1/2 cups hulled and halved strawberries
2/3 cup packed brown sugar
1/3 cup cornstarch
1 teaspoon groung cinnamon
2/3 cup rice flour
5 tablespoons coconut oil
1/2 cup granulated sugar
3 tablespoons brown sugar
1/8 teaspoon coarse salt
Blend first six ingredients in processor. Add coconut oil. Using on/off turns, cut in until very coarse meal forms. Mix ice water and vinegar and slowly add to dough. Blend until moist clumps form (about 15 pulses), adding more ice water by teaspoonfuls if dough is dry. Place processor container with dough in freezer for 3 minutes. Gather dough into a ball; flatten into disk on a piece of floured plastic wrap and set aside.
Preheat oven to 375 degrees F. Roll out dough using a piece of plastic wrap on both the top and bottom of the disk to a 12-inch round. Transfer dough to a 9-inch tart pan with removable bottom. Cut off overhang. Freeze crust until firm, about 10 minutes.
Place all filling ingredients in medium bowl; gently toss to combine and set aside.
Place all topping ingredients in a medium bowl. Using fingers, quickly blend mixture until small pea-size pieces form. Mixture will be dry.
Pour filling into crust and sprinkle with topping. Place pie plate on a large rimmed baking sheet and bake until crust is dark golden and filling is bubbling, about 1 hour and 15 minutes. Transfer to a rack and cool completely before serving. Can be refrigerated for 3 days.
*Modified recipe from Martha Stewart at http://www.marthastewart.com/900667/strawberry-rhubarb-pie-ginger-crumb-topping