Good recipes for crumb cake include Martha Stewart's New York crumb cake and blueberry crumb cake from the Food Network. Both recipes call for a streusel made from brown sugar, flour, butter, cinnamon and nutmeg.
Make blueberry crumb cake by whisking together 1/4 cup of granulated sugar, 1/3 cup of light brown sugar, 1 teaspoon of ground cinnamon and 1/8 teaspoon of ground nutmeg and then adding 1 stick of unsalted melted butter and 1 1/3 cups of all-purpose flour to make the streusel. To make the batter, beat together 6 tablespoons of softened unsalted butter and 3/4 cup of sugar, and mix in 2 room temperature eggs, 1 teaspoon of vanilla extract, 1/2 teaspoon of grated lemon zest and 2/3 cup of sour cream. In another bowl, whisk 1 1/4 cups of all-purpose flour, 1 teaspoon of baking powder, 1/4 teaspoon of baking soda and 1/2 teaspoon of salt. Add the dry ingredients to the butter mixture, and fold in 1 cup of fresh blueberries.
Pour the batter into a round baking pan, and sprinkle the streusel over the top. Bake the cake at 350 degrees Fahrenheit for 40 to 50 minutes. Sprinkle the cooled cake with confectioners' sugar to taste.