Heat a large cooking spray coated frying pan over medium-high heat. Season both sides of lamb with 1/8 teaspoon salt and 1/8 teaspoon pepper. Lay lamb in pan and cook 2 minutes per side. Take lamb out of pan and reserve in a warm place.
Combine 1/8 teaspoon salt, 1/8 teaspoon pepper, onion, and garlic in the same pan and cook 2 minutes.
Smash fennel seeds in a plastic bag, using a rolling pin. Mix fennel seeds, capers, and tomatoes to the pan and let boil. Place lamb back into pan, lower heat, cover, and simmer 6 minutes or until preferred degree of doneness.