Manischewitz acquired Horowitz-Margareten Matzo and manufactures Goodman matzo. Oat and spelt matzo with kosher certification are produced. It is usually flank steak boiled and served with vegetables, broth, and sometimes matzo balls. At the Passover seder, simple matzo made of flour and water is mandatory. After baking, matzo may be ground into fine crumbs, known as matzo meal. It may be leavened or unleavened (e.g. matzo). Instead of matzo meal, they use potato starch in cakes and other dishes. Consequently, the eating of matzo figures prominently in the Passover Seder. During Passover some American Jews eat matzo and other foods that conform to this restriction. Flavored varieties of matzo are produced commercially, such as poppy seed- or onion-flavored. Whole wheat, bran and organic matzo are also available. Oat matzo is generally suitable for those who cannot eat gluten. In addition to matzo, Manischewitz-labeled foods include cookies, pasta, and soups. Rabbi Haim Halberstam of Sanz ruled that machine-made matzo were chametz.