1 medium yellow squash, sliced into 1/4-inch-thick rounds
Kosher salt
1 cup shredded part-skim mozzarella
1/4 cup grated Parmesan
Cooking spray
Twelve 6-inch corn tortillas
4 scallions, sliced
1 cup salsa verde
1 large ripe tomato, sliced 1/4 inch thick
One thawed 9-ounce package frozen chopped spinach, squeezed dry