Streusel Coffee Cake

Streusel Coffee Cake
(found on about.com)This is an easy streusel coffee cake, baked in a square or round layer-cake pan.
INGREDIENTS:
Topping:
1/2 cup brown sugar
1/4 cup sifted all-purpose flour (sift before measuring)
1/4 cup butter, room temperature
1 teaspoon cinnamon
.
Cake:
1 1/2 cups sifted all-purpose flour (sift before measuring)
2 1/2 teaspoons baking powder
1/2 teaspoon salt
1 egg, beaten
3/4 cup sugar
1/3 cup melted butter
1/2 cup milk
1 teaspoon vanilla extract
PREPARATION:
Topping. In small mixing bowl, combine topping ingredients. Blend with fork until crumbly. Set aside.
Sift 1 1/2 cups sifted flour with baking powder and salt into a bowl. In a medium bowl, beat together beaten egg and 3/4 cup sugar and 1/3 cup melted butter.
Add milk and vanilla. Stir in flour mixture and mix well.
Pour batter into a greased and floured 8-inch square or 9-inch layer-cake pan. Sprinkle topping crumb mixture evenly over batter. Bake at 375° for 25 to 30 minutes, or until cake tests done. Partially cool in pan on wire rack. Cut coffee cake into squares while still warm.