Combine all the spices in a small bowl, including paprika, dried oregano, cayenne, cumin, salt, pepper, and onion powder.
Pat fish dry with paper towels. Sprinkle seasoning on both sides of the fish, gently rubbing it into the flesh. Let the fish sit for 15 minutes at room temperature.
Heat oil in a large saute pan over medium-high heat. Add fish to the pan, laying them in an even layer without overcrowding. Cook until charred, about 4-5 minutes. Flip and cook on the other side until charred and the flesh easily flakes. Remove from heat and squeeze lemon on top, if desired.
Notes
You may need to adjust the cooking time according to the thickness of your fish. I used tilapia for this dish, which was about ½-inch thick.