Preheat oven to 400 degrees. Spray a baking sheet with cooking spray. In a mixing bowl, whisk together flour, baking powder, sugar, salt and baking soda. Add buttermilk and eggs and beat on low speed 30 seconds until combined, then beat 1 minute on high speed. Dough will be sticky and will have the appearance of frosting. With wet hands, scoop out 6 to 8 even portions of dough and place them on prepared baking sheet, mounding the dough slightly into a bun shape. Re-wet fingers and smooth the tops and sides of each bun. If desired, sprinkle with sesame seeds. Bake in preheated oven for 15 minutes or until golden brown. Allow to cool. Split to serve with hamburgers. Cook’s note: The dough is sticky, so do keep a bowl of water handy to wet your hands before scooping out the dough for each bun and smoothing out the tops.