Preheat oven to 425 degrees. Spray a muffin pan with cooking spray or line with muffin liners.
Make the crumble topping by mixing sugars, flour, butter, cinnamon, and cardamom with a fork until coarse crumbs form.
Make the muffins by combining the flour, sugar, salt, and baking powder in a large bowl. Whisk to combine.
In a small bowl, combine the oil, egg, and milk until well-mixed. Add vanilla and almond extract, and whisk to combine.
Slowly add the egg mixture to the flour mixture, then stir until just combined.
Fold in blackberries.
Divide batter evenly into muffin cups.
Evenly sprinkle crumble topping over each muffin.
Bake the muffins at 425 degrees for 5 minutes, then, without opening the oven door, reduce the oven temperature to 350 degrees and bake for an additional 15-18 minutes, or until a toothpick inserted in the center comes out clean. Side Note: This helps create a dome on top of the muffin.
Allow the muffins to cool for 5 minutes in the muffin pan, then transfer to a wire rack to continue cooling.