Preheat your oven to 350°.
Your monkfish should be nice and boned and filleted, but chances are you'll want to a) rinse them under cold water, b) feel for bones, and c) clean any of the excess fat from the filet. It's as easy as getting the excess fatty film off of a chicken breast - simply pull at it with the hand you don't use to cut with, and with the hand you do cut with, slide your knife between the fat/film and the filet, removing as much of it as you can. Clearly this is less about "oh no, fat on my food", and more "finishing up with cleaning the fish".
OK, now you'll want to cut 8 equal portions from your filet. Depending on the size of your filets, you'll likely have roughly 1½ inch thick pieces. Salt and pepper them all.
Here's a great place for a holding pattern, to crack open a beer, to change the music, or to get your Baby Spinach with White Beans and Pancetta and Twice Cooked Potatoes prepped and underway. If you are dropping the meal into a holding pattern, put your monkfish back in the fridge.
About 30 to 45 minutes before you plan to eat, you'll want to put your Twice Cooked Potatoes into your oven.
After about 10 minutes you'll want to start pan searing your monkfish. To sear your monkfish, set a cast iron (or large sauté) pan over medium-high to high heat, and add your olive oil and butter. As that gets to temperature, place your 8 monkfish pieces into the pan. All you want to do is sear the outside of them, not cook them all the way through, so after about a minute or so, as the outside starts to brown a tiny bit, go around the pan with a pair of tongs, turn them over (in the order you put them in the pan), toss in your chopped onion, and add your dry vermouth. After about another minute or so, turn them all back over again, and put the pan into your 350° oven with the potatoes.
Now you've got 20 - 25 minutes until plating. You'll want to check the monkfish at about 20 minutes, to see if it's ready. You'll know it is when a nice sharp paring knife goes into the center of the pieces without hesitation.
Once the 20 - 25 minutes are up and your fish is done, take the pan out of the oven (and be careful, as the pan will clearly be hot). Time to plate!
To plate, put a portion of your Baby Spinach with White Beans and Pancetta in the center of the plate, and lay 2 pieces of your monkfish tiled on top of it. Place 3 or 4 Twice Cooked Potatoes around the plate, scatter some of the onions that were roasting with the fish around the plate, and take a quarter of your roasted red pepper slices and make a little nest on top of the monkfish (and repeat for each plate). Squeeze a quarter of the fresh lemon juice over each plate, and voila, dinner is served.
Cline's 2003 California Zinfandel goes really nicely with this meal.