In a large saucepan, combine all of the ingredients. Bring to a boil.
Reduce heat; simmer, uncovered, for 20-30 minutes or until thickened. Store in the refrigerator.
Blackened Catfish
In a shallow bowl, mix together the black pepper, garlic powder, onion powder, paprika, parsley, cayenne pepper, kosher salt, oregano, and thyme until thoroughly combined.
Press the catfish fillets into the spice mixture to thoroughly coat.
Place a large cast-iron skillet over high heat. Put half of the butter into the skillet; set remaining butter aside.
When the butter in the skillet is smoking hot, lay the catfish fillets into the skillet. Cook until the spices are burned onto the fillets and the catfish is opaque and flaky inside, about 3 minutes per side. Pour remaining butter over the catfish.
Put it All Together
Top the catfish with the corn relish. Use as much or as little as you like!