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.
When I didn't slice it for jerky, I always cut the meat into ~1" cubes and slid it on a skewer and cooked it wrapped in aluminum foil on the grill along with mushrooms, peppers, small potatoes and whatever seasoning I preferred that day. I typically put a strip of bacon in there as well to keep it from sticking to the aluminum foil (mostly because it is good for your heart and soul...lol).
Found a really easy way to cook duck this season, think it is a Hank Shaw recipe. Take the duck breast w/skin on (used sprig) . Salt both side pretty well with Kosher salt and let sit for 1 hour to get to room temp. Use a skillet w/butter and stove set to medium to medium high. Cook skin side down for 6 minutes and turn and cook the other side at 3 minutes. Let stand for 5 minutes. Comes out tasting like the best steak you ever had.