Preheat over to 350. Saute onion in oil for about 5 minutes stirring frequently. Add zucchini and cook until soft.

Meanwhile toast the rolls open faced in the oven for appx 5 minutes.

Add marinara sauce to the pan with zucchini and onions and sprinkle with red pepper flakes.

Transfer zucchini mix onto 1/2 of each roll and sprinkle cheese on top.

Wrap individually in aluminum foil. Bake for 15 minutes in the preheated oven, until bread is heated through, rolls are soft, and cheese is melted.