Bring a large saucepan of water to a boil. Add the lemon juice, salt and the Swiss chard stalks and cook until tender, about 7 minutes. Using a slotted spoon, transfer the stalks to a baking sheet to cool. Add the chard leaves to the pan and cook, stirring, just until wilted, about 1 minute. Drain the chard in a colander and let cool slightly, then gently squeeze out the excess water. Using a fork, fluff up the chard leaves to eliminate clumps.