Preheat the waffle maker and preheat the oven to 200 degrees F. In a large bowl mix the flour, sugar, baking powder, and salt. Cut the vanilla bean down the middle lengthwise, and scrape out the seed paste.
Add the vanilla bean paste, eggs, oil, and yogurt to the bowl. Whisk well, then whisk in the seltzer water to thin out the batter.
Pour the batter into the waffle maker. Use enough batter to fill the griddle sections, without overflowing. Cook for 3-4 minutes, until the majority of the steam has stopped pouring out of the waffle maker. Then check the waffle for a golden brown color.
As the waffles come out of the waffle maker, place them directly on the warm oven racks, so they stay crisp. Serve with maple syrup, or lots of toppings waffle-bar style!