How to Make It
Heat 2 teaspoons oil in a large nonstick skillet over medium-high heat. Sprinkle fish evenly with 1/4 teaspoon salt. Add fish to pan, skin side up; cook 3 minutes or until lightly browned. Turn fish over; cook 4 minutes or until desired degree of doneness. Remove fish from pan; keep warm.
Return pan to medium-high heat. Add remaining 1 teaspoon oil and pancetta; cook 1 minute, stirring occasionally. Add onion, pepper, and garlic; cook 5 minutes or until pancetta is browned, stirring occasionally. Add tomatoes and vinegar; cook 3 minutes or until tomatoes soften, stirring frequently. Add remaining 1/8 teaspoon salt, stirring well. Serve sauce with fish.
While dishes all'amatriciana are traditionally made with guanciale (cured Italian pork jowl), we substituted pancetta, which is more readily available.