Southwestern Vegetarian Casserole

Name: Southwestern Vegetarian Casserole
Ingredients: Cooking spray , for the casserole dish; 2 teaspoons olive oil; 1 small red onion , diced; 2 medium yellow squash or zucchini, chopped; 8 ounces cremini mushrooms , stems trimmed and diced; 1 large red, orange, or yellow bell pepper , seeded and chopped; 1 jalapeño , seeded and diced, optional; 1/2 large bunch (about 3 cups tightly packed) curly leaf kale , stems removed and leaves roughly chopped; 3 cloves garlic , minced; 2 teaspoons chili powder , plus more to taste; 1/2 teaspoon kosher salt , plus more to taste; 1/2 teaspoon freshly ground black pepper; 2 (15-ounce) cans pinto or black beans , rinsed and drained; 1 ( 10 - ounce ) can diced tomatoes with green chilies , drained; 1 ( 7 - ounce ) can salsa verde; 2 1/3 cups ( 326 g ) all-purpose flour , divided; 1 tablespoon baking powder; 1 tablespoon sugar; 3/4 teaspoon kosher salt; 1/2 teaspoon baking soda; 4 tablespoons unsalted butter , cold and cubed; 1 1/2 cups buttermilk; 1 1/2 cups shredded sharp cheddar cheese , divided