1. Combine first 5 ingredients in a medium bowl. Add lamb, stirring to coat. Marinate in refrigerator 1 to 2 hours.
2. Soak skewers in water 30 minutes. Preheat grill to medium-high heat (350° to 400°).
3. Thread lamb, onion, tomatoes, and lemons evenly onto skewers. Grill skewers 5 minutes on each side. Serve with rice pilaf and Feta-Mint Dipping Sauce. Garnish, if desired.