Sift rice flour, tapioca starch, potato starch, yeast, guar gum, salt, and baking powder together in a bowl.
Place quinoa, sunflower seeds, almonds, and flax seeds in a coffee grinder. Grind until very fine. Transfer to the flour-starch mixture. Mix until new dry mixture is well combined.
Combine milk, eggs, egg whites, molasses, agave nectar, olive oil, and vinegar in the bowl of a stand mixer fitted with the paddle attachment; beat on low until well blended. Pour in dry mixture slowly, beating on medium-high and pushing dough down with a spatula as necessary.
Scoop dough into the prepared pan, spreading it evenly with a wet spatula. Sprinkle with sesame seeds. Fill a large bowl with boiling-hot water and place it in a microwave. Rest a cooling rack on top of the bowl. Place pan on top and cover the dough. Let dough rise until it reaches the top of the pan, about 1 hour 30 minutes.
Bake in the preheated oven until the top is golden and an instant-read thermometer inserted in the center reads 200 degrees F (93 degrees C), about 45 minutes. Let bread cool thoroughly before slicing with a serrated knife.