How to Make It
In a medium bowl, toss the tomatoes with the onion, basil and 1 tablespoon of the olive oil.
In a skillet, heat the remaining 2 tablespoons of oil until shimmering. Season the barramundi with salt and add to the skillet, skin side down. Cook over high heat until the skin is crisp, 3 minutes. Flip and cook over moderate heat until just white throughout, 2 minutes longer. Transfer to plates.
Place the limes in the skillet, cut side down. Cook over moderately high heat until browned; transfer them to the plates.
Stir the rice vinegar into the tomato salsa and season with salt. Spoon the salsa alongside the barramundi and serve.