Heat the oil over medium-high heat in a medium sauté pan. Place the fish in the pan and cook undisturbed for 4 to 5 minutes. Flip the fish, being sure to scrape up all bits of the pan-seared crust. Once flipped, squeeze the juice of ½ the lemon over top of the fillets. The fish may brown somewhat, but it should not burn. Allow the fillets to cook another 5 to 7 minutes and then remove the fish. Deglaze the pan with the lemon juice, adding the two tablespoons of butter. Once the butter has melted, quickly scrape up the brown bits of flavor. Toss in the cilantro, and add Stubb’s Pork Spice Rub to taste. Spoon a teaspoon of the rich lemony butter onto the fish and serve.