Preheat oven to 350°F. Lightly grease a 9-inch round cake pan.
In a medium bowl, stir together flour, oatmeal, sugar, cinnamon, nutmeg, baking powder and baking soda. Cut in butter with a pastry blender or fork until mixture is crumbly. Remove 1 1/2 cups of the oat mixture and set aside for topping.
In a small bowl, stir together sour cream, eggs and vanilla. Add sour cream mixture to remaining oat mixture and stir until well blended. Spread batter into prepared cake pan. Spoon apricot preserves evenly over batter. Sprinkle reserved oat topping over preserves.
Bake 50-55 minutes or until toothpick inserted into center comes out clean. Serve warm, sprinkled with powdered sugar, if desired.