Pat fillets dry and season with salt and pepper, 1/4 teaspoon each.
Heat 4 tablespoons of butter in a cast iron (preferred) skillet over medium heat.
Mix flour and cayenne in a plate and dredge fillets in flour mixture.
Cook skin side down until skin is golden brown and slightly crisp, about 4 minutes.
Turn fish over and cook until just cooked through and lightly golden, 1 to 2 minutes more.
Transfer fillets to a plate and tent with foil to keep warm.
Pour off cooking butter and wipe skillet with a paper towel, then return skillet to medium low heat with remaining butter, pecans and remaining salt and pepper.
Stir until butter starts to brown and pecans are golden but not burnt.
Remove from heat and stir in brown sugar and lemon juice until sugar dissolves.
Pour sauce over fish and enjoy!
I like to serve mine over a bed of quinoa and a sautéed vegetable.