In a large skillet, cook sausage, onions and red pepper over medium heat until meat is no longer pink; drain and set aside. In a large bowl, combine the flour, cornmeal, cilantro, baking soda, salt and thyme.
In another bowl, combine egg and buttermilk. Stir into dry ingredients just until moistened. Fold in cheese and sausage mixture.
Fill greased muffin cups two-thirds full. Bake at 375° for 25-30 minutes or until a toothpick comes out clean. Cool for 5 minutes before removing from pan to a wire rack. Serve warm. Refrigerate leftovers.