GFCF Blueberry Crisp

2 pints blueberries, rinsed and dried (about 5 cups)1 tsp. grated lemon peel plus 1 tsp. lemon juice1/4 cup sugar2 tbsp. tapioca starch1/4 tsp. nutmeg or mace1/3 cup All Purpose GF flour blend1/3 cup packed brown sugar1/4 tsp. nutmeg or mace1/4 cup dairy-free, soy-free margarine, such as Earth Balance1/2 cup quinoa flakes (or gluten-free oats or even uncooked buckwheat hot cereal)1/2 cup walnut