While the pasta is cooking, heat a large sauté pan over medium-high heat. Add 1 tablespoon of the oil and cook the onions until they start to brown and soften, approx. 5 minutes. Add the cabbage and thyme and continue to cook, stirring often until beginning to brown in spots (approx. 3 minutes). Deglaze the pan with the apple cider. Cover and cook until wilted for 2 minutes, then uncover and continue to cook until most of the cider has evaporated, another 5 minutes, stir in the tagliatelle.