Arrange a rack in the middle of the oven and heat the oven to 375ºF. Line a standard 12-well muffin tin with paper liners or coat with cooking spray.
Place 1 cup all-purpose flour, 1 cup whole wheat flour, ½ cup of the rolled oats, 1 teaspoon baking powder, 1 teaspoon ground cinnamon, ½ teaspoon ground cardamom, and ½ teaspoon baking soda in a medium bowl and whisk to combine.
Place 2 large eggs, 1 cup unsweetened applesauce, ⅓ cup canola or vegetable oil, ½ cup maple syrup, ¼ cup milk, 2 teaspoons vanilla extract, and ½ teaspoon kosher salt in a large bowl and whisk to combine. Add the flour mixture and fold with a flexible spatula until no streaks of dry flour are left.
Divide the batter evenly among the muffin wells (about ⅓ cup per well), they will be about ¾ full. Sprinkle with the remaining 2 tablespoons rolled oats (about ½ teaspoon per muffin).
Bake until golden brown on top and a tester inserted into the center of a muffin comes out clean, 18 to 22 minutes. Let cool for 5 minutes in the tin. If not using paper liners, run a thin knife around each muffin to loosen. Transfer the muffins to a wire rack and let cool for at least 15 minutes before serving.
