Cut each catfish fillet crosswise into 3 or 4 pieces. Combine the flour, cayenne pepper and salt in a shallow dish. Lightly dredge the fish in the flour mixture.
Whisk the vinegar, honey and water together in a small bowl and set aside.
Heat the vegetable oil in a large nonstick skillet over medium-high heat. Working in batches if necessary, add the fish in a single layer and fry until golden brown, about 3 minutes per side. Carefully transfer the fish to a paper towel-lined plate, wipe the excess oil from the skillet and reduce the heat to medium.
Add the vinegar-honey mixture, heat for 30 seconds, then return the catfish to the pan. Turn the fish pieces over once to coat with the sauce. Transfer to a serving platter and dust with a bit of additional cayenne if desired (see notes). Add the cashews to the remaining honey-vinegar mixture, stir to coat and scatter over the fish.
Notes
The honey reduces the effect of the cayenne's heat somewhat, so plan to adjust the seasoning a bit after the fish is glazed to suit your taste for heat.