Curried Vegetable and Chickpea Stew

Name: Curried Vegetable and Chickpea Stew
Ingredients: 1 teaspoon olive oil; 1 large onion, diced; 1 tablespoon kosher salt, divided; 2 medium red or yellow potatoes, diced; 1 tablespoon curry powder; 1 tablespoon packed brown sugar; 1 tablespoon peeled and grated fresh ginger; 3 cloves garlic, minced; 1/8 teaspoon cayenne pepper (optional); 2 cups low-sodium vegetable broth, divided; 2 (15-ounce) cans chickpeas, drained and rinsed; 1 medium green bell pepper, diced; 1 medium red bell pepper, diced; 1 medium head cauliflower, cut into bite-sized florets; 1 (28-ounce) can diced tomatoes with their juices; 1/4 teaspoon freshly ground black pepper; 1 (10-ounce) bag baby spinach; 1 cup coconut milk