This Perfect Plum Tart is, as you probably know by now, one of my most serious obsessions. And it is the one I adapted into a gluten-free version last night for my mom.
I did a bit of research and a foodie acquaintance sent me a helpful link to glutenfreegirl's tips for crafting a wheat-free version of all-purpose flour. In essence, you want a 60%-40% ratio of white to whole grain flours. GF white flours include those made from potato, tapioca, and white rice, while whole grain subs include nut and brown rice flours.
I'd read previously that potato flour helped maintain a degree of crumb and flake, and glutenfreegirl reminded me that because nut flours contain much more fat than other flours, you need to compensate by decreasing the amount of other fats added.
And lo, this flour blend came to pass. For 1 and 1/2 cups of all-purpose flour, I subbed: 1/2 cup oat flour, 1/4 cup hazelnut flour, 1/4 cup potato flour, 1/4 + 1/8 cup brown rice flour and 1/8 cup tapioca flour. To accommodate the hazelnut flour, I decreased the amount of vegetable oil in the recipe above by half; from 1/4 to 1/8. To replace the 2 tablespoons of all-purpose flour in the filling, I used more tapioca. A definite success!