Pat COD fillets completely dry with paper towels and allow to come to room temperature. Pat dry again and sprinkle with a little salt and pepper. Not too much salt here because the prosciutto is salty. Wrap the fillets with prosciutto. You want to wrap them tightly but gently so that you do not tear the prosciutto. If your prosciutto is in strips rather than sheets, overlap the strips. Melt 2 tbsp butter in a cast iron skillet or other nonstick pan over medium heat. Once butter is hot, add fillets and cook for 5 min per side or until the fish flakes easily with a fork. Remove the fillets to a cooling rack. This prevents the bottoms from getting soggy. With the burner still on medium, add 1 clove garlic, minced, to the pan and stir for about 30 seconds. Add 4 c. baby spinach, 2 tbsp capers, and 1 tsp lemon juice. Stir and cook for about 1-2 minutes. Just until the spinach has wilted. Move the spinach to plates, top with the fish and sprinkle with lemon zest.