Beat butter, sugar and egg until fluffy. Add ground wheat to the flour, poppy seeds, soda and salt. Mix 1/3 of dry mixture with butter mixture, then add 1/4 cup sour cream, then the remaining flour mixture. Continue to mix on medium speed for two minutes. Grease pan (bottom and sides) and dust with sugar. Spread batter over bottom and one inch up the sides. Combine all ingredients for topping and sprinkle over batter. Bake at 350º for 40-45 minutes. Cool.