Preheat oven to 425°F. Line baking sheet with parchment or foil.
Remove wilted outer leaves from cabbage.
Cut cabbage through core into 6 even wedges. Keep core intact.
Arrange wedges on baking sheet with space between.
Drizzle olive oil over both sides. Coat evenly.
Season both sides with salt, pepper, and garlic powder.
Roast 30 to 35 minutes. Flip at 15 minutes.
Cabbage is done when edges are golden and caramelized.
Make brown butter. Melt butter in saucepan over medium heat.
Cook butter 3 to 4 minutes, swirling pan, until golden brown and nutty. Watch carefully.
Remove from heat immediately. Add garlic and red pepper flakes.
Stir in lemon juice. Be careful of sizzle.
Remove cabbage from oven. Transfer to platter.
Brush brown butter generously over hot wedges.
Garnish with parsley and Parmesan.
Serve hot with lemon wedges.