1. Bring 8 cups of water to a boil in a large saucepan. Cut broccoli rabe into 2-inch pieces. Cook broccoli rabe in boiling water 2 minutes; drain.
2. Heat a large nonstick skillet over medium heat. Add 1 tablespoon olive oil to pan; swirl to coat. Add crushed red pepper and garlic to pan; cook 30 seconds, stirring occasionally. Add broccoli rabe to pan; cook 2 minutes. Stir in salt and black pepper.
3. Cut four 1-inch slices of refrigerated polenta; cut slices into 1-inch cubes. Heat a large cast-iron skillet over medium-high heat. Add 1 tablespoon olive oil to pan; swirl to coat. Add polenta; cook 8 minutes, turning to brown on all sides. Top broccoli rabe with croutons.