In a small saucepan over high heat, bring mango nectar and mango to a boil. As mango begins to break down, press down on it with a fork or potato masher, to mash it.
Continue cooking until mango cooks down to form a chunky puree, about 15 minutes. Remove half to serve as a sauce. Set the other half aside for dredging. On a large plate, mix together flour, cornmeal, sugar and salt.
Preheat a large skillet. Season salmon with salt and freshly ground black pepper. Brush glaze over top of salmon, then dredge in cornmeal mixture. Add oil and butter to skillet. Over high heat, sear salmon cornmeal mixture face down until golden, about 6 to 8 minutes for medium rare, flipping halfway through to crisp skin.