Separate the stems and leaves of 2 bunches rainbow chard; coarsely chop. Cook the stems, 1 sliced garlic clove and a pinch of salt in olive oil, covered but stirring occasionally, 6 minutes; transfer to a bowl. Cook the leaves, stirring, 5 minutes. Add 1/2 cup cream; simmer 3 minutes. Stir in the stems, lemon juice, salt and pepper.