Set your oven at 400°F. If your cod fillets need to be thawed out put them in bowl of water. They will be ready to go in about eight minutes. Put the potatoes in the microwave for about two to two and a half minutes. Rinse off and cut the ugly stump ends off of the asparagus spears. Cut up the potatoes into slices about 1/4" thick. Put everything into a large bowl. 

Add the olive oil, parmesan cheese, salt, pepper, lemon juice and dill weed (optional). Slide your hands under everything and gently toss it all to get everything coated with all of that good stuff. Line a sheetpan with aluminum foil. Spread everything out on the sheet pan. Pour any liquids left in the bowl all over it.  Put it in the oven.

After fifteen minutes poke things with a table fork. They just might be soft enough and ready to serve. If not give them another five minutes. Serve up and enjoy your One Sheetpan Codfish Fillet Dinner.