How to Make It
Combine buttermilk and 1 tablespoon granulated sugar in a small saucepan, stirring with a whisk. Cook over medium heat until a thermometer registers 110°. Remove from heat. Dissolve yeast in buttermilk mixture; let stand 5 minutes.
Weigh or lightly spoon flours, potato starch, and flaxseed meal into dry measuring cups; level with a knife. Combine flours, potato starch, flaxseed meal, xanthan gum, and next 4 ingredients in a large bowl; beat with a mixer at medium speed until blended. Add buttermilk mixture, oil, 1 tablespoon butter, 1 teaspoon vanilla, egg whites, and egg; beat at low speed until dough pulls away from sides of bowl.
Turn dough out onto parchment paper dusted with tapioca flour. Cover with an additional piece of floured parchment. Roll dough, still covered, into a 15 x 10-inch rectangle. Remove top sheet of paper; brush dough with remaining 2 tablespoons melted butter.
Combine brown sugar, remaining 1 tablespoon granulated sugar, and 1 teaspoon cinnamon in a small bowl, stirring with a whisk until blended. Sprinkle sugar mixture over butter. Sprinkle raisins over sugar mixture.
Beginning at short side, roll up dough tightly, jelly-roll fashion, while peeling away paper; pinch seam and ends to seal. Cut dough into 15 (1-inch) slices. Place slices in muffin tins coated with cooking spray. Cover with plastic wrap; let rise in a warm place (85°), free from drafts, 1 1/2 hours or until dough has risen to top of tins.
Preheat oven to 375°.
Bake at 375° for 20 minutes or until golden brown.
Combine powdered sugar and remaining ingredients; stir with a whisk until smooth. Remove rolls from muffin tins; drizzle with glaze. Serve warm.