Brine the boneless duck breast for 3-5 days in the fridge, changing the water daily. This gets rid of the blood and muddy flavor. When it's time to cook, take the meat out of the water and dry with paper towel. Tenderize the filets. Then season with salt, garlic powder, and pepper.
Put a cast iron skillet on the stove and turn the burner on to 4 (out of 10). Melt some butter in the skillet along with some avocado or olive oil. Once up to temperature, put the seasoned breast filets in the skillet and cook until medium rare (about 135 degrees internal). Don't overcook.
Let them rest for 3-4 minutes before serving. No sauce needed. It's great.