Whisk together pumpkin, yogurt, baking soda, egg yolk, and flour. Whisk egg whites with salt; fold into pumpkin mixture. Heat a large nonstick skillet coated with cooking spray over medium heat. Spoon in 1/3 cup batter for each pancake. Flip when tops are covered with bubbles and edges are slightly brown (about 3 minutes per side). Drizzle with syrup or honey.