Lemon Berry Bars

(Recipe and picture from Allergy Proof Recipes for Kids by Leslie Hammond and Lynne Marie Rominger page 194)

My aunt loves lemon bars, and she totally approves of these! Berries add not only flavor, but also nutritional value.
For Crust:
1/2 cup (120 ml) fresh lemon juice
1 teaspoon (1.7 g) lemon zest
1/2 cup (100 g) vegetable shortening
1 cup (125 g) white rice flour
1/2 cup (65 g) corn, tapioca, or arrowroot starch
1/2 cup (50 g) powdered sugar (contains cornstarch,
use corn-free recipe on page 103)
1/s teaspoon (0.6 g) baking powder
1/s teaspoon ( 0.75 g) salt
Lemon Filling:
1/2 cup (65 g) corn, tapioca, or arrowroot starch
1 1/4 cups (250 g) sugar
1 cup (235 ml) water
1 1/2 cups (355 ml) lemon juice
1 teaspoon (1.7 g) lemon zest
Berries
1 cup fresh (130 g) raspberries, blueberries, or blackberries

1. Preheat oven to 350°F(180°C, or gas mark 4).
2. To make the crust: Combine all crust ingredients in a food processor and process until dough forms into a ball. Press crust into a 9 x 13-inch (23 x 33-cm) baking pan. Bake for 25 minutes. Let cool.