Combine tomatoes and boiling water; let stand 30 minutes. Drain and slice.
Combine cornmeal and 1/8 teaspoon black pepper in a large saucepan. Gradually add 3 cups broth and 1 cup water, stirring constantly with a whisk. Bring to a boil; reduce heat to medium, and cook 20 minutes, stirring frequently. Remove from heat; keep warm.
Place a large nonstick skillet coated with cooking spray over medium heat until hot. Add onion and bell pepper; sauté 10 minutes or until tender. Add sun-dried tomatoes and garlic; sauté 1 minute. Stir in 1 cup broth and greens; bring to a boil. Cover, reduce heat, and simmer 15 minutes or until greens are tender. Stir in 1/8 teaspoon black pepper. Spoon the polenta into center of each of 4 plates, and top evenly with greens mixture. Sprinkle with cheese.