Preheat oven to 350 degrees. Grease 2 (9x13–inch) glass baking dishes. In a small bowl, whisk together flour, baking powder, salt, and cinnamon. In bowl of stand mixer, beat the butter at medium speed and then add sugar, eggs, and vanilla and blend until smooth. Reduce speed to low and add flour mixture, blending until well mixed. Stir in nuts. Divide dough into 4 equal pieces. On a large sheet of waxed paper dusted with flour, roll 1 portion of dough to 10 inches wide and 12 inches long.
