Braised Chicken and Spinach Soup with Pita Chips

Name: Braised Chicken and Spinach Soup with Pita Chips
Ingredients: 1 small red onion, thinly sliced; 2 Tbsp. fresh lemon juice; Kosher salt; 2 Tbsp. extra-virgin olive oil; 2 Tbsp. unsalted butter; 1 large yellow onion, thinly sliced; 4 garlic cloves, thinly sliced; 8 green cardamom pods, lightly crushed; 1 tsp. ground coriander; ¼ tsp. crushed red pepper flakes; 1 large bunch mature spinach, trimmed, or one 10-oz. package frozen whole-leaf spinach, thawed; 1 lb. skinless, boneless chicken thighs; Steamed white rice and pita chips (for serving)