Combine brown sugar, paprika, salt, oregano, garlic powder, and cumin in a small bowl. Mix until evenly blended. Sprinkle the spice mixture over both sides of tilapia and rub in gently with your fingers.
Place a large enamel-coated or non-stick pan over medium-high heat, and drizzle in a thin layer of olive oil. When hot, place fish in the pan and cook for 2-3 minutes per side, until they are cooked through (145 degrees F and easy to flake with a fork) and have a dark reddish-brown crust on the outside. Spritz with lemon juice.
Remove from pan and serve right away with extra lemon wedges and a sprinkle of fresh parsley or oregano, as desired.
Notes
For more heat: Add a pinch of cayenne pepper to the spice mixture.
Cookware: You can use a large cast-iron skillet, rather than a non-stick pan, but be sure it is well-seasoned and has a good slick of cooking oil, else it will be more difficult to flip the fish and to clean up afterwards.