Slide a rack in the middle of the oven and crank the heat to 375°F (190°C). Coat a standard 12-cup muffin pan with the nonstick cooking spray.
Whisk the 2 1/4 cups all-purpose flour, 2 teaspoons baking powder, 1 teaspoon kosher salt, 1/2 teaspoon ground cinnamon, 1/2 teaspoon ground nutmeg, and 1/4 teaspoon ground cardamom in a medium bowl.
Beat the 1 stick unsalted butter and 3/4 cup dark brown sugar in a large bowl using a hand-held mixer on medium speed until light and fluffy, 4 to 5 minutes.
Add the 1 large egg and 1/2 teaspoon vanilla extract and beat until smooth.
Alternate adding the flour mixture and 1 cup whole milk in three batches, beginning and ending with the flour. Divvy the batter among the muffin cups.
Bake the dirt bombs, turning the pan once halfway through, until a toothpick inserted into the center comes out clean, 18 to 23 minutes. Let the dirt bombs cool 5 minutes in the pan and then move them to a wire rack.