2 cups unbleached all-purpose flour2 teaspoons baking powder1½ teaspoons baking soda1½ teaspoons ground cinnamon1 teaspoon salt¼ teaspoon ground allspice1 cup canola oil1 cup granulated sugar¾ cup light brown sugar, packed4 large eggs1 teaspoon vanilla extract3 cups finely grated peeled butternut squash1 cup drained crushed pineapple1 cup toasted chopped walnutsCream cheese frosting (optional)One 8-ounce package cream cheese, softened½ cup (1 stick) butter, softened1 teaspoon vanilla extract2 to 2½ cups confectioners' sugar, siftedPreheat the oven to 350 degrees. Butter and flour a 9-by-13-inch baking pan.Sift together the flour, baking powder, baking soda, cinnamon, salt and allspice.In a large mixing bowl, combine the oil, granulated sugar and brown sugar. Beat until well combined. Add the eggs one at a time, beating well after each addition. Add the vanilla. Continue to beat until fluffy. Gradually add the dry ingredients, mixing just until the batter is smooth and blended. Fold in the squash, pineapple and walnuts. Spoon the batter into the prepared pan.Bake for about 35 minutes, until a cake tester inserted in the center of the cake comes out clean.On a wire rack, cool completely before frosting.For frosting:In a medium bowl, beat together the cream cheese, butter and vanilla. Add 2 cups of the sugar and beat until smooth. If the frosting is too thin, mix in the additional ½ cup sugar and beat until smooth.Spread evenly over cooled cake. Makes about 2 cups.