Heat the oven to 350º and grease a 12-cup bundt pan (or two 9- by 5-inch loaf pans, or two 6-cup bundt pans). To make the cinnamon filling, place the cinnamon, butter, brown sugar, and flour in a small bowl and mix with your fingers. Set aside.

For the coffee cake, combine the flour, baking powder, baking soda, and salt in a large mixing bowl. In a separate large bowl, cream the butter and sugar, then beat in the eggs, one at a time. Beat in the vanilla extract and the sour cream. Gradually add the dry ingredients, beating well after each addition.

Spoon half of the coffee cake batter into the large bundt pan (or, if you're using two smaller pans, one quarter of it into each pan). Crumble the cinnamon mixture over the top. Pour in the remaining batter and then use a table knife to swirl the cinnamon throughout. Bake for 50 to 60 minutes (or 35 to 40 minutes for the smaller loaves) or until a toothpick inserted in the cake comes out clean.

Invert the coffee cake onto a rack and cool it thoroughly before dusting with confectioners' sugar. Place the cake on a doily-covered plate, wrap it in red or green cellophane, and tie with a bow. Serves 10 to 12.