Marinate: Toss cod with harissa, honey, 1/2 lemon juice, and a pinch of salt. Set aside.
Sauté & simmer: Heat an oven-safe skillet over medium heat. Sauté leeks and garlic for 3-4 minutes until soft. Add zucchini, spinach, Calabrian chilies, vegetable broth, bouillon cube, and 1 lemon's juice. Let it reduce and simmer for 5 minutes.
Add beans: Stir in the cannellini beans and simmer together for another 2-3 minutes.
Broil: Nestle the marinated cod on top of the stew. Transfer the pan under the oven broiler on high for 6-8 minutes, until the fish is opaque, flaky, and lightly caramelized.
Serve: Whisk together the yogurt, chopped jalapeños, brine, dill, cilantro, lemon juice, and salt. Drizzle generously over the top before serving.