Coat a 9-inch round cake pan with cooking spray; set aside.
Bring water to a boil in a large saucepan over medium-high heat. Reduce heat; add cornmeal, stirring constantly with a whisk. Cook 5 minutes, stirring frequently. Remove from heat, and stir in cheese, 1/4 teaspoon salt, pepper, and cilantro. Pour into prepared cake pan. Press plastic wrap onto surface, and chill 1 hour or until firm.
Heat oil in a large nonstick skillet over medium-high heat. Add onion, and sauté 2 minutes. Add eggplant, squash, carrot, and jalapeño; sauté 4 minutes, stirring frequently. Stir in chili powder, tomatoes, and 1/4 teaspoon salt; bring to a boil. Reduce heat; simmer 15 minutes.
Invert the polenta onto a cutting board; cut into 4 wedges. Place on a baking sheet coated with cooking spray. Broil 5 minutes on 1 side until golden. Place on plates, and top with ragout.