For roasted potatoes: Preheat oven to 400 degrees F. Toss potatoes in olive oil, garlic powder, salt and pepper. Place them in a single layer on a baking pan. Bake for 20-25 minutes, until golden. Set aside.
Fill a fish kettle ¾ of the way full with water. Add sliced lemons, onions, fish stock, and garlic cloves. Place on stove top over medium-high heat.
Place poaching tray in kettle and place fennel on top of tray.Wait for water to boil. Add fish filets (make sure they are completely covered with water) and cover with lid. Reduce heat to low, simmer for 15 minutes.
While fish is cooking, mix salad ingredients together, addenough oil to dress. Season with salt and pepper to taste.
Carefully remove fish from kettle and place on salad.
Serve with lemon slices.