Put fruit in 2 1/2 quart dish. Drip lemon juice over the fruit, if desired. Sprinkle 1/4 cup sugar over
Make batter: Cream together melted margarine (or oil) and 1/2 cup sugar. Add milk, then rice flour, tapioca flour, potato starch, xanthan gum and baking powder. Mix well and spread over fruit. This will be thick.
Topping: Mix 1/2 cup sugar and thickener (sweet rice flour or cornstarch) in bowl. Sprinkle over batter. I think you could use less here. Slowly pour hot water over all
Bake at 375 °F for close to an hour.
Notes
Sweet rice flour is found in the Asian section. This is a thickener, so I imagine you could also use tapioca flour, etc. Originally called for cornstarch.
If you don't have a safe margarine, you can substitute oil, and the recipe will work. I think it's a bit better with melted margarine, though.
It may look strange when you put water on but it really does work.
Substitutions
Those who can have wheat could replace the 1/3 cup each rice flour, potato starch, and tapioca starch with 1 cup wheat flour, and omit the xanthan gum.
If not avoiding corn, one of the starches can be replaced with corn starch.
Do not omit the sweet rice flour or cornstarch in the final sugar topping.
Butter and Margarine: Butter is a dairy product made from cow’s milk. Margarine typically contains milk or soy, but there are milk-free and soy-free versions available.
Corn Substitutions: Corn is a common ingredient in products. Starch, modified food starch, dextrin and maltodextrin can be from corn. Consult with your physician to find out which corn derivatives you need to avoid. Many corn-free options are available in the US. Find out more about corn substitutions.
Gluten: Gluten is a protein found in specific grains (wheat, spelt, kamut, barley, rye). Other grains are naturally gluten-free but may have cross-contact with gluten-containing grains. Look for certified gluten-free products if you need to avoid gluten. Find out more about wheat and gluten substitutions.
Milk and Soy Substitutions: Alternative dairy-free milk beverages and products will work in most recipes. Find out more about milk substitutions and soy substitutions.