Place a large piece of foil on top of a sheet pan. Toss chard and chickpeas with vinegar, olive oil, capers, garlic, and salt. Spread out on one half of the sheet pan.
Top chard and chickpeas with salmon. Season salmon with some salt and pepper and top with lemon slices.
Enclose salmon and seal foil tightly. (Note: You may have to really compress the chard to fit inside the foil packet. It will seem like a lot, but will cook way down.)
Transfer sheet pan with salmon to oven and cook until salmon flakes easily with a fork, 25 to 30 minutes. (This will vary a bit depending on the thickness of your salmon. You can pull back the foil a bit to check on it.)
While salmon cooks, whisk together yogurt, lemon juice, mustard, honey, and a pinch of salt.
Serve creamy lemon sauce over salmon and greens. Enjoy!
Salmon - I like to buy pre-sliced salmon filets because they are so easy to serve. You can also buy whole piece of salmon (about 1.5 lbs for 4 servings) and just slice it when serving. Skin-on or skinless salmon will work fine in this recipe.