PREHEAT oven to 375°F. Place each tilapia filet on a large square of foil. Drizzle each filet with 1 tbsp lemon juice, then evenly sprinkle the spices and lemon zest over the fish. Top each filet with 1 tsp of butter and wrap the foil tightly around the fish. Place the foil pouches on a baking sheet.
HEAT the ghee in a large skillet and sauté the onion and pancetta for 3-4 minutes, until the onion softens and the pancetta begins to crisp. Add the garlic and continue sautéing for another minute. Add the celery and crushed tomatoes to the pan. Season with the salt, pepper, and smoked paprika.
Cover and simmer for 10 minutes.
WHILE the celery simmers, place the fish in the oven and bake for 15 minutes. After the celery has simmered for 10 minutes covered, uncover, reduce heat to medium-low, and continue simmering for 8-10 minutes, until most of the liquid has cooked off.
REMOVE the fish from the oven and the foil. Plate and enjoy.