Preheat
the oven to 350°F/180°C/gas
4.
Butter and flour a
10-inch (25-cm) spring form pan.
Sift the flour, baking powder, ginger, nutmeg,
baking soda, and salt into a large bowl.
Beat the oil, brown sugar, and eggs in a large bowl
with an electric mixer at high speed until creamy.
Beat in the carrots, hazelnuts, sunflower seeds, and
the dry ingredients.
Spoon the batter
into the prepared pan.
Bake for
70-80
minutes,
or until a toothpick inserted into the center comes
out clean.
Cool in the pan for 10 minutes. Loosen and remove
the pan sides. Invert the cake onto a rack. Loosen
and remove the pan bottom and let
cool completely.
Frosting: Beat the cream
cheese, butter, and orange zest in a medium bowl
until fluffy. Beat in the confectioners' sugar.
Spread the cake with the frosting.