Garlic Roasted Brussels Sprouts

2 pounds fresh Brussels sprouts, cut in half (or quarters if sprouts are large)
6 garlic cloves, rough chopped
1 medium red onion, sliced
2 tablespoons extra virgin olive oil
1 teaspoon kosher salt
1 teaspoon fresh ground black pepper

Preheat oven to 450°F.  Line a baking sheet with aluminum foil.