Preheat oven to 400°.
Weigh or lightly spoon flours into dry measuring cups; level with a knife. Combine flours, baking powder, baking soda, and salt in a large bowl; cut in butter with a pastry blender or 2 knives until mixture resembles coarse meal.
Combine pumpkin, yogurt, and 1 egg white, stirring with a whisk. Add to flour mixture; stir just until moist.
Turn dough out onto a lightly floured surface; knead lightly 4 times with floured hands. Pat dough into an 8-inch circle on a baking sheet lined with parchment paper.
Cut dough into 12 wedges, cutting into but not through dough. Brush remaining 1 egg white over top of dough. Sprinkle dough with cheese and pumpkinseeds, pressing lightly to adhere.
Bake at 400° for 20 minutes or until golden. Slice scones along score lines with a serrated knife. Serve warm.