Microwave carnitas according to package directions. When warm, shred meat with forks. Cover and set aside.
To prepare tortillas, heat a griddle or grill pan to medium-high heat. Fill a shallow bowl or plate with water. Dip each side of tortilla in water and immediately place on grill pan. Warm tortilla 1 minute each side, then place in foil to keep warm. Repeat for each tortilla.
To assemble tacos, layer tortilla with carnitas, salsa, diced onions and a drizzle of crema. Garnish with chopped cilantro and lime wedges, and serve.