Cornbread with tenders

1 cup frozen diced onion, red and green bell peppers, and celery 2 small garlic cloves, pressed 1 tablespoon canola oil 1 1/2 pounds butternut squash, peeled,[...]

4 tablespoons unsalted butter 3 cups cornmeal 2 teaspoons cream of tartar 2 teaspoons salt 1 teaspoon baking soda 3 cups low-fat milk 4 large eggs 9 ounces[...]