Tex-Mex Summer Squash Casserole

2 1/4 lb. summer squash, quartered lengthwise & thinly sliced crosswise (about 10 C.)
2/3 C. finely chopped sweet onion
4 oz. can chopped green chilies
2 medium jalapenos, seeded & finely chopped
1/2 tsp. salt, or to taste
2 1/4 C. grated extra-sharp cheddar cheese, divided
1/4 C. all-purpose flour
3/4 C. mild salsa
4 scallions, thinly sliced for garnish
1/4 C. finely chopped red onion for garnish

Preheat oven to 400 degrees. Coat a 13" X 9" baking dish with cooking spray.
Combine squash, onion, chilies, jalapenos, salt, and 3/4 C. cheese in a large bowl. Sprinkle with flour; toss to coat. Spread mixture in the prepared baking dish and cover with foil.
Bake until bubbling and squash is tender, 35-45 min. Spoon salsa over the casserole & sprinkle with remaining 1 1/2 C. cheese.
Bake uncovered until golden and heated through, 20-30min. Sprinkle with scallions and red onion.

Helpful Tip: To make ahead, prepare as directed above. Cover and refrigerate up to 2 days. Reheat, covered with foil at 350 degrees for about 40 min. Garnish just before serving.