Peel the beet, chop it into rough pieces, and process it in the food processor until smooth.
1 medium beet
In a large mixing bowl, combine the dry ingredients (flour, sugar, cornstarch, cocoa, baking powder, baking soda, and salt)
1½ cup (193 grams) all-purpose flour, ½ cup (100 grams) granulated sugar, ¼ cup cornstarch, 2 tablespoons unsweetened cocoa, 2 teaspoons baking powder, ¼ teaspoon baking soda, ½ teaspoon salt
Into the measuring cup with the buttermilk, add the eggs, vanilla extract, vinegar, and cooled butter and whisk it all together.
1 cup buttermilk, 2 large eggs, 1 teaspoon vanilla extract, 1 teaspoon white vinegar, 6 tablespoon (3 ounces) unsalted butter
Add the beets and liquid ingredients to the dry ingredients and stir only until the dry ingredients are mixed in. Do not over stir.
Preheat your waffle iron and cook the waffles as directed.