Stir together butter, shallot, zest, lime juice, chiles, and salt in a bowl.
Pat dry the fillets and sprinkle with salt. Heat oil in a 12-inch nonstick skillet over moderately high heat until just smoking, then saute the fillets, turning over once with a spatula until golden and just cooked through (4 to 5 minutes). Transfer to a plate. Serve each warm fillet with a dollop of chili lime butter. Garnish with cilantro leaf.