3 sprays cooking spray, divided
12 oz uncooked lean pork tenderloin, cut into 1-to-1 1/2-inch chunks
1/2 t. table salt, divided
1/2 t. freshly ground black pepper, divided
3 small Yukon gold potatoes, peeled and cut into 1-inch chunks
1 medium onion, halved and thinly sliced
3/4 c. water, or more if necessary, divided
1 medium yellow pepper, cut into 1-inch chunks
8 oz cremini mushrooms, halved or quartered lengthwise (about 3 cups)
3/4 t. dried rosemary, or to taste
1 c. marinara sauce