In a small bowl, mix marinara sauce, garlic powder and herbes de Provence. Arrange half of the polenta slices in a greased 8-in. skillet. Top with half of the sauce; sprinkle with 3/4 cup cheese. Repeat layers.
Cook, uncovered, over medium heat 12-14 minutes or until bubbly. Cover; cook 2-3 minutes longer or until cheese is melted.