/* Contenedor principal del formulario */

input[type="submit"][value="SUBMIT"] {
  font-size: 0;
  position: relative;
}
input[type="submit"][value="SUBMIT"]::before {
  content: "ENVIAR";
  font-size: 16px;
  position: absolute;
  left: 0;
  right: 0;
  text-align: center;
}