Combine buttermilk, butter and lemon juice in a bowl and set aside.
Mix together the salt, pepper, dillweed and crushed cereal in a flat bottom bowl. Dip each piece of fish into the buttermilk, butter and lemon mixture first then roll in the cereal and spice mix until coated.
Place fish fillets in a greased 13x9 pan and bake at 350°F until fish flakes easily with a fork, approximately 20 to 30 minutes, depending on thickness of the fish fillets.
Notes
To Make Buttermilk: put 1 tsp vinegar into measuring cup and add whole milk (or milk alternative) to bring to 1/2 cup - let stand 5 minutes.