Preheat broiler. In a large skillet, cook and crumble beef and lamb with onion over medium-high heat until meat is no longer pink, 5-7 minutes; drain., Mix together next nine ingredients. Add to meat mixture; cook, stirring occasionally, until well blended and heated through. Remove from heat., In batches, spritz both sides of tortillas with cooking spray and place on a baking sheet; broil 4-5 in. from heat until crisp and lightly browned, 45-60 seconds per side. Spread meat mixture over tortillas. Serve with lemon wedges.