Preheat oven to 375Â°.
Combine flour and next 7 ingredients (through nutmeg) in a large bowl; stir with a whisk. Make a well in center of mixture.
Combine brown sugar, oil, rind, juice, and eggs; stir with a whisk. Add egg mixture to flour mixture; stir just until combined. Spoon batter into 18 muffin cups with paper liners. Bake for 17 minutes or until muffins spring back when touched in center.