Preheat oven to 325F
Slice shallots into thin wedges, long ways. Cut rhubarb in half lengthwise and cut into 4 inch pieces.
In a large ovenproof skillet, heat oil over medium heat. Saute shallot for 3-4 minutes, until just tender and fragrant. Add rhubarb, sauting for one minute.
Push shallots and rhubarb to the outer edges of the pan and place salmon in the center.
Season salmon and rhubarb with a little salt and pepper. Drizzle maple syrup just over rhubarb ( do not skimp here- see notes). Drizzle sherry wine ( or balsamic) over the rhubarb ( see notes). Sprinkle with ½ of the thyme leaves ( saving ½ for garnish at the end). Place in the oven and roast for 15 minutes. Check salmon after 10- and pull if necessary ( see notes) -continue cooking rhubarb for full 15 mins or when it is fork tender.
In another skillet, heat oil over medium heat. Add garlic and sauté until golden about 2 minutes. Add chard stems, sauté for 1-2 two minutes then add remaining chard and season with salt, pepper, lemon zest and a little squeeze of lemon. Set aside.
Plate the salmon and divide rhubarb shallot mixture among the two plates. Add the wilted chard.
Spoon the flavorful liquid from the salmon pan over the salmon itself. Garnish with remaining sprigs of thyme.