Preheat oven to 350°F. Stir together milk and cornmeal; set aside.

Heat oil in a large skillet over medium-high. Add onion, garlic, and bell pepper; cook, stirring occasionally, until the vegetables begin to soften, about 8 to 9 minutes. Add beef; cook, stirring often, until meat crumbles and is no longer pink, about 7 minutes.

Stir beef mixture into cornmeal mixture. Stir in tomato sauce, corn, olives, chili powder, salt, and black pepper. Transfer to a lightly greased 13- x 9-inch glass or ceramic baking dish.

Bake in preheated oven until set and well browned around edges, 55 minutes to 1 hour. Remove from oven; sprinkle with cheese. Return to oven, and bake until cheese melts, 3 to 4 minutes. If desired, top servings with a dollop of sour cream and sprinkle with cilantro.