1 pound (4 sticks) unsalted butter, at room temperature
1 pound granulated sugar
1 pound eggs, at room temperature
1 pound all-purpose flour, plus for the pan
2 cups confectioners' sugar
1 1/2 teaspoons cinnamon
2 to 3 tablespoons milk
The cake will keep at room temperature, covered with plastic, for up to 2 days.