Put brussel sprouts on a baking sheet; Cut the apples into chunks, sprinkle apples on the baking sheet. Pour the cut onions all around the baking sheet to mix in.
Drizzle the olive oil over the brussel sprouts mixture, then add the salt, black pepper and the garlic powder.
Toss gently to mix thoroughly. Make sure in even layer on the baking sheet.
Roast in the oven for about 20 minutes.
Remove from oven and put into a serving dish.
To finish, sprinkle with the lemon zest and then pour on the lemon juice to serve. Grind black pepper at the end.
