Preheat the oven to 325°F. Butter a 9-inch square pan.
In a large bowl, use an electric mixer to combine the butter and sugar. Beat in the eggs slowly, one at a time. Add the remaining ingredients and mix well to incorporate.
Pour the batter into the prepared pan. Bake for 45 to 50 minutes, or until a toothpick inserted into the center comes out clean.