Preheat oven to 350°. Grease and flour a 10-in. fluted tube pan. In a large bowl, beat butter and sugar until crumbly. Add eggs, 1 at a time, beating well after each addition. Beat in lemon juice and extract. In another bowl, whisk flour, baking powder, baking soda and salt; add to creamed mixture alternately with sour cream, beating after each addition just until combined. Stir in squash.
Transfer to prepared pan. Bake until a toothpick inserted in center comes out clean, 50-55 minutes. Cool in pan 10 minutes before removing to a wire rack to cool completely. Combine glaze ingredients; pour over cake.
