1Whisk lemon juice and lemon zest together in a bowl.
2Mix flour, salt and pepper together in a resealable gallon-size plastic bag.
3Pat Swai fillets dry with a paper towel.
4Place fillets in the bag mixture, 1 at a time, and shake to coat.
5Heat large skillet over medium heat; add butter and heat until lightly browned.
6Place coated fillets in the browned butter; cook until lightly browned on the edges and fish flakes easily with a fork, 2 -3 minutes per side.
7Transfer fish to a plate, reserving butter in the skillet.
8Pour lemon juice mixture into skillet with reserved butter, cook and stir until light sauce forms, 2-3 minutes.
9Pour sauce over fish and garnish with parsley.