Preheat oven to 375°F (190°C).
Cut cabbage into 8 wedges, leaving the core intact.
Heat olive oil in a cast iron skillet over medium-high heat.
Sear cabbage wedges until golden brown on both sides, then remove and set aside.
Add butter to the skillet, then sauté red onion and garlic until soft and fragrant.
Deglaze the skillet with chicken broth, scraping up browned bits.
Whisk in cream cheese until smooth and fully combined.
Stir in heavy cream, sun-dried tomatoes, dried herbs, salt, pepper, and optional red pepper flakes; simmer briefly.
Mix grated Parmesan cheese into the sauce until melted and incorporated.
Return cabbage wedges to the skillet, spoon sauce over each wedge.
Cover skillet and bake for 45 minutes.
Uncover, baste cabbage with sauce, and bake for an additional 15–20 minutes until tender.
Garnish with fresh parsley before serving.