Spiced Braised Lamb with Carrots and Spinach

1 lb boneless lamb cubes 1 teaspoon black pepper 1 1/2 teaspoons salt 1 to 3 tablespoons olive oil 1 large onion, chopped 1 celery rib, chopped 3 garlic cloves, finely chopped 4 teaspoons ground cumin 2 teaspoons ground coriander Read on!