Squeeze juice from 2-3 limes into a small bowl. Turning a fork into the flesh of the fruit will help get extra juice and pulp from the limes. Remove cilantro leaves from the stems and chop. Add to bowl.
Mix lime juice and cilantro with garlic powder and black pepper. Pour marinade into a large, covered bowl with the tilapia filets. Let sit for 30-60 minutes.
Add the oil to a large skillet pan. For extra flavor, add some of the marinade to the pan. Cook the fish on medium, for 3-4 minutes.
Flip the fish and cook for a remaining 3-4 minutes. Once cooked through, it is ready to serve!