1 2/3 cups all-purpose flour
1 tablespoon baking powder
1 teaspoon salt
1 teaspoon ground cinnamon
1 cup milk
1 cup vegetable oil
1/2 teaspoon vanilla extract
1 1/4 cups minced onion
Place flour in a large bowl. Stir milk into flour. Stir flour mixture into milk; beat until blended. Fold in onion. Pour into baking dish.
Cover baking dish with lid and place in refrigerator or freezer. Cover loosely with aluminum foil. Let stand for 1 hour, or overnight.
Preheat oven to 375 degrees F (190 degrees C).
Remove foil and bake in preheated oven for 1 hour, or until golden brown. Remove foil and bake for an additional hour or until toothpick inserted in center of dish comes out clean. Cool completely before cutting into strips.