Wash the Swiss chard. Separate the leaves from the stems and cut them into 1 cm wide strips and cut the stems into fine strips. Clean the carrots and cut into fine strips.
Heat the butter in a pan. Sauté shallots, carrots and chard stalks in it for 5 minutes, turning over high heat. Squeeze in the garlic, season with sugar, salt and pepper. Add the chard leaves and cook covered for another 5 minutes over low heat.
Stir in the crème frâiche and reduce to a creamy consistency for 3 minutes over a medium heat. Season the vegetables with 1-2 tablespoons of lemon juice and the lemon peel and serve hot.