1. Adjust oven rack to middle position and heat oven to 250°F. Set wire rack in rimmed baking sheet and place baking sheet in oven. Whisk flour, sugar, salt, buttermilk powder, and baking soda in large bowl to combine. Whisk sour cream, eggs, vanilla, and oil in medium bowl to combine. Gently stir seltzer into wet ingredients. Make well in center of dry ingredients and pour in wet ingredients. Using a rubber spatula, gently stir until just combined. Batter should remain slightly lumpy with streaks of flour.

2. Heat waffle iron and bake waffles according to manufacturers instructions (use about 1/3 cup for 7-inch round iron). Transfer waffles to rack in warm oven and hold for up to 10 minutes before serving with butter and maple syrup.

Makes about eight 7-inch round waffles