Preheat the oven to 355 degrees F (175 degrees C). Prepare 2 pieces of parchment paper large enough to cover a 9-inch round tart pan.
Whisk rice flour, buckwheat flour, potato starch, tapioca starch, white sugar, and dark brown sugar together. Cut in butter with your fingers until fully incorporated. Mix in egg and egg yolk by hand. Knead until the dough comes together to form a ball.
Roll out the dough between the 2 sheets of parchment paper until it is approximately 1/2-inch thick and large enough to cover the bottom and rim of the tart pan. Place the crust in the pan. Remove the top sheet of paper to poke holes with a fork. Replace the paper. Fill the pan with pie weights or dried beans.
Bake the tart shell on the bottom rack of the oven until slightly browned, 12 to 15 minutes. Remove and set aside to cool, removing the weights. Keep the oven on.
Meanwhile, whisk together ricotta, white sugar, dark brown sugar, and egg yolks in a bowl until smooth and creamy. Pour ricotta mixture over the crust and smooth out with a rubber scraper. Top with fresh blueberries.
Bake until the blueberries and the ricotta cream are bubbly and beginning to brown, 35 to 40 minutes. Allow to cool to set before serving.