Preheat the oven to 400 degrees F. Trim the Brussels sprouts by slicing off the ends and remove any yellow outer leaves. Cut the Brussels sprouts in half lengthwise. 

2. Place the Brussels sprouts in an 8 x 8-inch baking pan. Drizzle with olive oil and sprinkle with the sea salt, black pepper, onion powder, fresh thyme leaves and optional garlic powder if using. Toss until the Brussels sprouts with your hands to evenly coat them with the seasoning. 
3. Place the Brussels sprouts in the oven and roast for 20 minutes. Add an optional touch of lemon juice or apple cider vinegar just before serving. The cooked Brussels sprouts will keep for up to 4 days when stored covered in the refrigerator.