1. Heat oven to 425 degrees F. Coat a 14-inch pizza pan with nonstick cooking spray. Dust with 1 tbsp of the polenta.
2. Bring 6 cups water to boiling. Add 1 1/4 tsp of the salt and the garlic powder. Slowly add polenta in a thin stream, whisking constantly. Reduce heat to medium and cook, stirring frequently, 5 minutes.
3. Remove from heat and stir in 3 tbsp of the Parmesan. Spread onto prepared pizza pan. Set aside.
4. Heat oil in a large, lidded skillet over medium heat. Add garlic and cook 1 minute. Add broccoli rabe and 1/4 cup water. Cover and cook 3 minutes. Uncover, increase heat to medium-high and cook an additional 3 minutes until just tender.
5. Spread ricotta over polenta, leaving a 1-inch border. Scatter broccoli rabe and garlic over ricotta. Top with remaining 3 tbsp Parmesan.
6. Bake at 425 degrees F for 15 minutes until cheese is melted. Season with remaining 1/4 tsp salt; cut into wedges and serve.