Whisk vinegar, juice, honey, and pepper flakes together in a small bowl. Heat a 12-inch nonstick skillet. Add oil. Season the salmon with salt and pepper and cook, skin side up, without moving until well browned for 4 to 5 minutes. Flip and cook until all but the very center is opaque, 2-3 minutes, then transfer to a platter and cover to keep warm.

WIPE. OUT. THE. PAN. Then lower the heat. Carefully pour the balsamic mixture into the pan, as it may splatter. Simmer until thick and syrupy, about 5 minutes, then whisk in the butter, season as desired, and pour over the salmon and serve.

Note: Recipe may make too much sauce for 2 salmon fillets. But gotta try it first! If it ends up being too much, halve the sauce ingredients but keep the salmon at 2 fillets.