Cut the chard into 2-inch sections, separating stems from leaves.
In a sauté pan, heat the olive oil over medium heat. Add the garlic and stir quickly (do not let it burn) for about 15 seconds. Drop in the stems and toss for 30 seconds. Add in a little water and cover for another 20-30 seconds.
Add the leaves and toss. Sauté until wilted, adding a touch more water if necessary.
Drain and remove Swiss chard. Toss in lemon zest and Parmesan, if using.