Preheat oven to 400°.
Lightly spoon flour into dry measuring cups; level with a knife. Combine flour and next 6 ingredients (through apple-pie spice) in a large bowl. Make a well in center of mixture. Combine milk, butter, vanilla, and egg in a small bowl; add to flour mixture, stirring until just moist. Gently stir in blackberries.
Spoon 1/4 cup batter into each of 17 paper-lined muffin cups coated with cooking spray. Bake at 400° for 16 minutes. Sprinkle muffins evenly with granulated sugar; bake 3 minutes or until muffins spring back when touched lightly in center. Cool in pans 10 minutes on wire racks.
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