Preheat oven to 400°F. Line a baking tray with foil and set aside.
Clean Brussels sprouts, trim the bottoms, and remove any spoiled leaves. Cut sprouts in half lengthwise, through the stem.
In a large bowl, toss sprouts with olive oil, garlic powder, salt, and pepper.
Add to baking tray in a single layer and bake for 30 minutes.
Increase oven temperature to 450°F. Sprinkle Brussels sprouts with lemon juice if using. Bake for an additional 5-10 minutes to brown, being careful not to burn the sprouts.
Notes
Refrigerate leftovers up to 4 days, or store in freezer bags and freeze for up to 12 months.